REVIEW Obesity and the Polycystic Ovary Syndrome

Home , Hyperandrogenism, Hyperinsulinemia

A Gambineri1, C Pelusi1, V Vicennati1, U Pagotto1 and R Pasquali1*

1Endocrinology Unit, Department of Internal Medicine, S. Orsola-Malpighi Hospital, University Alma Mater Studiorum, Bologna, Italy

The polycystic ovary syndrome (PCOS) is a condition characterized by hyperandrogenism and chronic oligo-anovulation. However, many features of the metabolic syndrome are inconsistently present in the majority of women with PCOS. Approximately 50% of PCOS women are overweight or obese and most of them have the abdominal phenotype. Obesity may play a pathogenetic role in the development of the syndrome in susceptible individuals. In fact, insulin possesses true gonadotrophic function and an increased insulin availability at the level of ovarian tissue may favour excess androgen synthesis. Obesity, particularly the abdominal phenotype, may be partly responsible for insulin resistance and associated hyperinsulinemia in women with PCOS. Therefore, obesity-related hyperinsulinemia may play a key role in favouring hyperandrogenism in these women. Other factors such as increased estrogen production rate, increased activity of the opioid system and of the hypothalamic-pituitary-adrenal axis, decreased sex hormone binding globulin synthesis and, possibly, high dietary lipid intake, may be additional mechanisms by which obesity favours the development of hyperandrogenism in PCOS. Irrespective of the pathogenetic mechanism involved, obese PCOS women have more severe hyperandrogenism and related clinical features (such as hirsutism, menstrual abnormalities and anovulation) than normal-weight PCOS women. This picture tends to be more pronounced in obese PCOS women with the abdominal phenotype. Body weight loss is associated with beneﬁcial effects on hormones, metabolism and clinical features. A further clinical and endocrinological improvement can also be achieved by adding insulin-sensitizing agents and=or antiandrogens to weight reduction programmes. These obviously emphasize the role of obesity in the pathophysiology of PCOS. International Journal of Obesity (2002) 26, 883 – 896. doi:10.1038=sj.ijo=0801994

Keywords: obesity; polycystic ovary syndrome; hyperandrogenism; metabolic syndrome

Definition of the polycystic ovary syndrome compared to the general population favored the hypothesis The polycystic ovary syndrome (PCOS), one of the most that, at the basis of this syndrome, a genetic component may common causes of ovulatory infertility, affects 1 – 5% of exist whose inheritance is still a matter of controversy.3 women. Over the years, after the first description by Stein However, the heterogeneous clinical characteristics of this and Leventhal in 1935,1 this syndrome has been defined in syndrome indicate that a more complex interaction between different ways. Finally, in 1990 the National Institutes of genetic and environmental factors may cause this disorder.3 Health (NIH) established the new diagnostic criteria for this Several features of the ‘metabolic syndrome’, particularly disorder, which are based on the presence of hyperandrogen- insulin resistance and hyperinsulinemia, are inconsistently ism and chronic oligo-anovulation, with the exclusion of present in the majority of women with PCOS. This represents other causes of hyperandrogenism such as adult-onset con- an important factor in the evaluation of PCOS throughout genital adrenal hyperplasia (CAH), hyperprolactinemia and life, and implies that the PCOS by itself may not be a androgen-secreting neoplasms.2 The observation of an hyperandrogenic disorder exclusively related to young and increased prevalence of PCOS among family members as fertile women, but may have some health implications later in life.4 Obesity is very common clinical feature in women affected by PCOS. In fact, approximately 50% of PCOS women are overweight or obese5 and the history of the *Correspondence: R Pasquali, Unita` Operativa di Endocrinologia, weight gain frequently precedes the onset of oligomenorrhea Dipartimento di Medicina Interna, Policlinico S. Orsola-Malpighi, Via and hyperandrogenism, suggesting a pathogenetic role of Massarenti 9, 40138, Bologna, Italy. obesity in the subsequent development of the syndrome. E-mail: [email protected] Received 25 May 2001; revised 3 December 2001; Interestingly, some recent data have introduced the idea that accepted 20 December 2001 in obese PCOS women the disorder may originate during Obesity and the polycystic ovary syndrome A Gambineri et al 884 intrauterine life, depending on the mother and also on birth late adrenal steroidogenesis. In vitro studies have shown that weight.6 However, this fascinating hypothesis needs to be insulin may also increase 17a-hydroxylase and 17 – 20 lyase validated by further studies. activity in the adrenals either directly13 or potentiating the This review will try to highlight the pathophysiological responsivity of the enzyme to adrenocorticotropin hormone mechanisms by which obesity may influence PCOS develop- (ACTH) stimulation.14 ment and=or maintenance. In addition, we will summarize The findings described above, together with the clinical the modern concepts in the management of the obese PCOS. evidence that a huge number of PCOS women show a condition of insulin resistance and hyperinsulinemia, suggested that insulin may play a pivotal role in the promotion Pathogenetic mechanisms by which obesity may or the maintenance of PCOS.7,15 The link between hyper- promote or maintain PCOS insulinemia and hyperandrogenism in PCOS women is sum- Insulin marized in Table 1. A molecular cause of insulin resistance Together with the well-known actions at the level of classical has been identified as an excessive phosphorylation of serine target organs such as liver, adipose tissue and muscles, residues of the insulin receptor. This molecular defect, which insulin plays a role in the regulation of other tissues=organs, has been described in at least 50% of PCOS women,15 reduces rgans, particularly the ovary, besides the pituitary and the the tyrosine kinase activity of the insulin receptor, thereby adrenal gland. At ovarian level, insulin acts by interacting decreasing the signal transduction pathway. Alternatively, with its own receptor and by the insulin growth factor (IGF) mechanisms such as mutations in insulin receptor gene or receptor type I, which have been detected in human models insulin receptor substrate-1 (IRS-1), an intracellular protein throughout all ovarian compartments, as granulosa, thecal phosphorylated under the influence of the insulin-receptor and stromal tissues.7 It has also been definitively proved that tyrosine kinase,16,17 a cellular adenosine depletion,18 adefi- insulin is able to stimulate ovarian steroidogenesis both in ciency in peroxisome proliferator-activated receptor-g (PPAR- granulosa and thecal cells. In fact, insulin increases 17a- g)19 or a defect at the post binding level, involving glucose hydroxylase and 17 – 20 lyase (both components of the transport,16 have also been proposed. In the presence of P450c17 enzyme system) activity8 and stimulates the expres- peripheral insulin resistance, pancreatic b cell insulin secre- sion of 3b-hydroxysteroid dehydrogenase in human lutei- tion increases in a compensatory fashion, leading to a nized granulosa cells.9 Conversely, the role of insulin on hyperinsulinemic state.20 In addition, primary alterations aromatase activity is rather discordant, in vitro studies having of insulin secretion independent of the presence of insulin demonstrated either a stimulatory10 or a lack of effect.9 In resistance,21 as well as defective insulin clearance in periph- addition, insulin appears to increase the sensitivity of pitui- eral tissues, have been reported in PCOS.22 By these mechan- tary gonadotropes to gonadotropin releasing hormone isms the hyperinsulinemic state can be further increased. (GnRH) action7 and to potentiate the ovarian steroidogenic Interestingly, although in classical peripheral tissues insulin response to gonadotropins, by mechanisms probably related is able to down-regulate its receptors,23 their expression is to an increase of the luteinizing hormone (LH) receptor conversely preserved in the ovary even in the presence of number.7 Moreover, insulin is able to inhibit hepatic sex insulin resistance and hyperinsulinemia,7 probably by the hormone binding globulin (SHBG) synthesis11 and both interaction between insulin and other regulatory factors hepatic and ovarian IGF binding protein-1 (IGFBP-1) synth- such as gonadotropins, sex steroids, IGFs and IGF binding esis, which bind sex steroids and IGFs, respectively,12 to proteins (IGFBPs).24 On the other hand, insulin may amplify regulate ovarian growth and cyst formation7 and to modu- its effect during the insulin resistance state by upregulating the IGF receptor type I.7 Some aspects of insulin action in obesity resemble those Table 1 Links between hyperinsulinemia and hyperandrogenism in seen in PCOS. Many patients with obesity are insulin resis- PCOS women tant and hyperinsulinemic, particularly when the abdominal Insulin causes a direct stimulation of ovarian androgen secretion, possibly phenotype is present. The mechanisms by which obesity through stimulatory effects on the 17a-hydroxylase=17-20 lyase and on may induce an insulin-resistance state have been extensively 3b-hydroxysteroid dehydrogenase enzymes summarized elsewhere.25 Briefly, enlargement of adipose Insulin decreases levels of SHBG, with concomitant elevation of free tissue mass, in particular of visceral fat depot, increases the androgen tissue availability Insulin decreases IGFBP-1 production, both in the liver and in the ovary availability of several metabolites (ie free fatty acids (FFA), Insulin upregulates ovarian IGF receptor type I with amplification of IGF-I, lactate, etc), which are able to affect the secretion and the IGF-II and insulin actions in the ovary metabolism of insulin as well as its peripheral action.26 Insulin increases the LH ovary receptor number and sensitizes LH secreting Insulin resistance in obesity can also be related to tumor pituitary cells to GnRH stimulation Insulin promotes ovarian growth and cyst formations necrosis factor-a (TNF-a) and to leptin, both products of Insulin can cause a direct stimulation of adrenal androgen secretion, possibly adipose tissue. TNF-a mediates serine phosphorylation of through stimulatory effects on the 17a-hydroxylase=17-20 lyase enzyme IRS-1,27 which has been shown to interfere with the action Insulin may increase the 17a-hydroxylase=17-20 lyase adrenal enzyme of both insulin and IGF-I, by inhibiting insulin receptor and response to ACTH type I IGF receptor tyrosine kinases respectively, and by

International Journal of Obesity Obesity and the polycystic ovary syndrome A Gambineri et al 885 stimulating IGFBP production.7 TNF-a can also inhibit sig- events resulting in the exaggeration of the effects of both naling through PPAR-g.7 Leptin may contribute to the insu- insulin and IGFs at ovarian level. No differences in serum lin resistance of obesity via mechanisms similar to TNF-a.7 IGF-I and IGF-II levels between PCOS and non-affected The impact of obesity on insulin resistance and hyperinsu- control women have been described, regardless of body linemia in PCOS is reviewed in the paragraph on Metabolic weight, but obese PCOS women have lower serum IGFBP-1 abnormalities. To summarize, obesity seems to amplify the levels than their normal-weight counterparts.7 This probably degree of insulin resistance and hyperinsulinemia in PCOS. represents an insulin-related effect, as a negative correlation In fact, although insulin resistance has been described to between insulin levels and serum IGFBP-1 concentration has affect obese and also most normal-weight PCOS women, been described.7 However, serum IGF bioavailability is obese women, particularly those with the abdominal obesity higher in normal-weight than obese PCOS women.30 This phenotype, are usually more insulin resistant and more is probably due to differences in GH levels between non- hyperinsulinemic than their normal-weight counterparts.5,18 obese and obese PCOS women. In fact, the occurrence of an These findings therefore indicate that obesity may sub- increase in GH pulse amplitude, mainly attributed to an stantially contribute to determine the insulin resistant state increased pituitary stimulation by the hypothalamic in PCOS. However, the possibility that a component of growth hormone releasing hormone (GHRH) has been insulin resistance in PCOS women may be present regardless demonstrated in normal-weight PCOS women.31 Conversely, of the obese state cannot be excluded. a reduction of GH pulse amplitude and of 24 h mean GH levels, probably caused by a decreased GH response to GHRH stimulation, has been observed in obese PCOS patients.31 Growth hormone (GH)-IGFs Similar findings have been found in obese non-PCOS IGF-I and IGF-II are well known effectors of ovarian func- women, therefore suggesting that the development of hypo- tions. They exert their action through activation of two types somatotropinism in obese PCOS women may be an obesity- of receptors as type I and II, which are present in granulosa, dependent event.32 In addition, in obese subjects an theca and stroma cells of the human ovary.28 The ovarian increased GH metabolic clearance rate has been described.33 effects of both IGF-I and IGF-II in humans are summarized in Although mechanisms have not been fully elucidated, there Table 2. Briefly, they are able to stimulate ovarian progester- is evidence that elevated FFA levels and increased insulin one (P) and oestradiol (E2) secretion and to increase the levels may play a pivotal role in determining reduced GH aromatase activity7 and androgen production in granu- levels in obesity. Therefore, it is realistic to speculate that losa – luteal and thecal human cells, respectively.29 Activa- similar mechanisms may play a role in obese PCOS women. tion of both type I and type II IGF receptors has also been In summary, IGFs may be involved in the pathogenesis of associated with a reduction of IGFBP peripheral levels, as a the hyperandrogenism in the PCOS. In normal-weight PCOS result of an inhibition of IGFBP-1 and IGFBP-2 production women IGF bioavailability seems to be increased by various and of an increased activity of IGFBP protease. A reduction of mechanisms such as insulin-induced hepatic and ovary IGFBP level may increase the bioavailability of IGFs, indu- IGFBP-1 suppression and GH-induced hepatic IGF stimula- cing as a net effect a more potent stimulus of IGF-I and IGF-II tion.30 On the contrary, in obese PCOS, IGF-1 bioavailability at the level of target tissues. The IGF=IGFBP system is regu- seems to be reduced in comparison to their normal-weight lated by insulin. In particular, insulin amplifies the effects of PCOS counterpart, although relatively higher than in non- itself and of IGFs as well by increasing the number of type I affected women because of the combination of low GH and IGF receptors. Insulin is also able to inhibit IGFBP-1 produc- high insulin levels. Therefore, the IGF=IGFBP system in obese tion, leading to a further increase in bioavailable IGFs. Thus, PCOS women seems to be differently expressed with respect hyperinsulinemia may lead to a self-perpetuating cycle of to their normal-weight counterpart, suggesting a different

Table 2 Ovarian actions of IGF-I and IGF-II in humans

Granulosa (granulosa=luteal) cells Theca cells=explants Follicles Promotes: Promotes: Promotes:

Aromatase activity and mRNA Androstenedione production Oocyte maturation?

Basal E2 and P secretion Testosterone production FSH-stimulated E2 and P secretion DNA synthesis DNA synthesis Cellular proliferation IGFBP-4 proteolysis IGFBP-5 production ?IGFBP-2 proteolysis Inhibits: IGFBP-1, IGFBP-2 production

From Poretsky et al,7 with permission.

International Journal of Obesity Obesity and the polycystic ovary syndrome A Gambineri et al 886 pathogenetic impact of this system in obese and non-obese the P450c17 enzyme represents the main mechanism lead- PCOS women. In particular, it could be suggested that ing to ovarian hyperandrogenism occurring in the great insulin resistance and hyperinsulinemia may play a central majority of PCOS patients.38 Whether hyperactivity of the role in obese PCOS patients, whereas abnormalities of the P450c17 enzyme system is a primary event or secondary to IGF-IGFBP system may be important in normal-weight PCOS peripheral or central factors is still unclear. The role of women. neuroendocrine factors, particularly LH, will be discussed below, whereas that of peripheral factors, including insulin and the IGF=IGFBP system, has been described above. Briefly, SHBG increased insulin and free IGF bioavailability in PCOS SHBG is a glycoprotein produced in the liver acting as a women can produce hyperandrogenism directly by stimulat- carrier for different sexual steroid hormones. SHBG displays ing ovarian androgen production. As discussed elsewhere, a higher binding affinity for testosterone (T) and dihydro- insulin also decreases levels of SHBG, with elevation of free 34 testosterone (DHT) and a lower affinity for E2. The con- androgens, and amplifies the ovary LH effect. In addition, centrations of SHBG are stimulated by a number of factors insulin and IGFs may affect follicle maturation and atresia. such as cortisol, estrogens, iodothyronines and GH, and In fact, both insulin and IGFs seem to be involved in the decreased by androgens, insulin, prolactin and IGF-I.35 Diet- interruption of the normal follicle maturation favouring the ary factors may also affect SHBG concentrations, since both formation of atretic follicles.7 The granulosa cell maturation short-term and long-term high lipid intake have been shown arrest and the resulting deficient aromatase activity of atretic to decrease SHBG serum levels.5 Mechanisms by which high follicles may, in turn, be directly responsible for the lipid intake decreases SHBG concentrations are still increased ovarian androgen secretion. Other factors, such unknown, even if a role of the increasing insulin levels as the follicle stimulating hormone (FSH)-inducible inhi- after such diets has been proposed to explain this clinical bin – follistatin – activin system, produced by the granulosa finding. Decreased basal SHBG concentrations are detected cell and acting on the theca cell, may be implied in the in PCOS women, with a more pronounced SHBG reduction dysregulation of ovarian steroidogenesis in PCOS women. found in obese PCOS, and in particular in obese women Indeed, some in vitro studies have demonstrated that inhibin presenting the abdominal phenotype.5 Due to its inhibiting stimulates ovarian androgen production.39 As reported effect on SHBG synthesis in the liver, insulin plays a domi- above, a phosphorylation of serine residues of the insulin nant role in reducing SHBG levels in insulin-resistant PCOS receptor15 may be a factor leading to insulin insensitivity patients, particularly in those with abdominal obesity.11 A and, therefore, compensatory hyperinsulinemia in PCOS number of physiopathological36 and epidemiological stu- women. Interestingly, the same disorder seems to be respon- dies37 showed a significant negative correlation between sible for the increased activity of the human P450c17 system SHBG and insulin blood levels in different physiological as well.40 Therefore, the serine phosphorylation of both the and pathological conditions. Lower SHBG levels in obese P450c17 enzymatic system and the insulin receptor may PCOS women may, in turn, be responsible for increased represent a single primary genetic disorder which may bioavailability of sex hormones at the level of target tissues. contribute to explain the association between hyperandro- Theoretically, this may, in turn, be partly responsible for the genism and insulin resistance in PCOS women.15 development of the abdominal obesity phenotype. In fact, Hyperandrogenism of adrenal origin often coexists with exposure to androgens has been found to increase visceral fat that of ovarian origin in many PCOS women. Provided in either obese and normal-weight post-menopausal classical forms of CAH are excluded, mechanisms by which women.38 an increase in androgen synthesis occurs in the adrenal In summary, obesity, particularly the abdominal pheno- gland are still unknown, although central and peripheral type, may directly worsen hyperandrogenism in women factors have been variously proposed to explain it. Central with PCOS by reducing SHBG serum levels, therefore increas- factors may involve a pituitary hyper-responsiveness to cor- ing the delivery of free androgens at the level of peripheral ticotropin releasing hormone (CRH).41 Among peripheral tissues. This can be explained by the degree of prevailing factors, insulin seems to exert an important role, by its hyperinsulinemia and, possibly, by other factors, including ability to increase the activity of 17a-hydroxylase and 17 – dietary lipids. 20 lyase in the adrenals both directly13 and through a facilitation of ACTH stimulation.14 Interleukin-6 (IL-6) has also been proposed to modulate intra-adrenal steroidogen- Androgens esis, by the ability of this cytokine to increase DHEA secre- A key step in androgen formation is the regulation of tion.38 An interesting hypothesis was produced by Rodin and P450c17 enzyme which is located in the ovarian theca- collegues,42 who reported that the activity of 11b-hydroxys- interstitial cells and in the adrenal gland.38 Expression and teroid dehydrogenase enzyme, which interconverts cortisol activation of P450c17 gene in ovary and=or adrenal cortex is to its inactive compound cortisone, may be increased in regulated by a number of hormones or growth factors PCOS women. The enhanced oxidation of cortisol in PCOS including LH, ACTH, insulin and IGFs.38 Hyperactivity of may result in compensatory overstimulation of the hypotha-

International Journal of Obesity Obesity and the polycystic ovary syndrome A Gambineri et al 887 lamic – pituitary – adrenal (HPA) axis that could, in turn, SHBG concentrations and, probably, alterations of the corti- increase the adrenal androgen formation. Similarly to these sol – cortisone metabolic pathways. The role of leptin in this findings in PCOS subjects, an altered cortisol metabolism has context is still under debate. In fact, leptin appears to also been detected in obese patients.43 directly stimulate ovarian 17a-hydroxylase activity.56 How- Obesity seems to amplify the degree of hyperandrogenism ever, whether leptin excess could play a role in the develop- in PCOS. Previous studies have shown that obese PCOS ment of the hyperandrogenism in obese PCOS women women have total44 and free T45 levels higher with respect remains to be elucidated by future studies. to non-obese PCOS. Abdominal obesity may also further worsen the hyperandrogenic state in PCOS women.46,47 This is not an unexpected finding, since the increase of Estrogens body weight and fat tissue in women is associated with In women with PCOS, high levels of estrone (E1) and of free several abnormalities of sex steroid balance. Such changes E2 have been detected as a result, at least in part, of reduced involve androgens and SHBG, their main carrier protein. concentrations of SHBG.34 The acyclic production of extra- Obese women have increased androgen production glandular estrogen may lead to a positive feedback on LH associated with an enhanced metabolic clearance rate, secretion and a negative feedback on FSH secretion, giving although the balance of these alterations allows the main- an increase of the circulating LH=FSH ratio.57 The elevated tenance of normal circulating androgen levels.5,48 However, levels of LH substantially contribute to the development of the percentage of free androgen fraction tends to be higher hyperplasia of the ovarian stroma and thecal cells, further in obesity, particularly in the abdominal phenotype, due to increasing androgen production and in turn providing more the reduction of SHBG concentration.49 Abdominal obesity substrate for extraglandular aromatization and perpetuation could therefore be defined as a condition of a relative ‘func- of chronic anovulation. Obesity per se represents a condition tional hyperandrogenism’. of ‘functional hyperestrogenism’. In fact, the estrogen pro- Hyperandrogenism per se may play a role in favouring duction rate positively correlates with body weight and the insulin resistance and the simultaneous development of the amount of body fat.5 Moreover, due to reduced SHBG synth- abdominal obesity phenotype in PCOS women. In fact, esis and lower circulating SHBG concentrations, the free E2 androgens may induce the insulin-resistance state both fraction increases in obese women, thus enhancing exposure through the activation of the lipolytic cascade, leading to of target tissues to unbound estrogens.5 Estrogen metabolism an increased serum FFA release, and the modification of the is also altered in obese women, due to a decreased formation muscle histological structure. The local stimulation of FFA of inactive E2 metabolites, specifically 2-hydroxyestrogens, 5 efflux is mainly described to occur in the visceral fat depot, and to a higher production of E1 sulfate. As a final result, an due to the high androgen receptor density present at this increased balance of active to inactive estrogens is often level.50 The direct effect of T at the level of muscle structure detected in obese subjects. This may represent an additional has been described in female rats51 where the administration mechanism amplifying the positive feedback on LH secre- of T induced a decrease in red, oxidative, insulin-sensitive, tion, therefore favouring increased ovarian androgen synth- type I muscle fibers, an increase in white, glycolytic type II esis, at least in selected obese PCOS women. However, as less insulin-sensitive fibers, a reduction of capillary density discussed below, this still represents a controversial issue. and an inhibition of glycogen synthase system. Such alterations have been subsequently confirmed in biopsies derived from women affected by hyperandrogenism and severe insu- Neuroendocrine factors lin resistance state.52 The close interaction between hyper- LH. An elevation of circulating LH concentration is incon- androgenism and development of insulin resistance state has sistently found in PCOS women and seems to occur as a been further confirmed by the results obtained in clinical result of a GnRH-mediated increase in the amplitude and trials in which administration of antiandrogen therapy such frequency of pulsatile LH secretory pattern.58,59 On the other as flutamide and spironolactone led to a partial but signifi- hand, an increased LH bioactivity is an almost invariable cant improvement of the insulin-resistance state.53 – 55 Alto- feature of PCOS, but the mechanism responsible for this gether, these data seem to definitively point to an important alteration still remains unclear.60 It is a matter of debate role of hyperandrogenism in the development of insulin whether the increase of gonadotrophins, when present, may resistance in PCOS women. Thus, a vicious circle between be attributed to a primary abnormality of the hypothala- hyperandrogenism and hyperinsulinemia could be suggested mic – pituitary axis or may be secondary to alterations in to represent the specific biological basis for the development peripheral signaling. As reported in the previous paragraph, of the obese-PCOS phenotype in women. the elevation of circulating LH concentration may be due to In summary, obesity further increases the degree of hyper- inappropriate estrogen feed-back to neuroendocrine cen- androgenism in PCOS women. Consequently, obese PCOS ters.57 In particular, several data seem to indicate that hyper- women tend to be more hyperandrogenic than their normal- oestrogenemia not counteracted by P, as occurs during weight counterparts. Specific mechanisms of action of obe- anovulation state, may favor the LH hyper-responsiveness sity include more severe hyperinsulinism, more reduced to GnRH.59 In fact, both spontaneous ovulation or

International Journal of Obesity Obesity and the polycystic ovary syndrome A Gambineri et al 888 exogenous P administration are associated with a normal- HPA axis. As reported above, many PCOS women present ization of LH secretion in PCOS women.58 Whether this with increased adrenal androgen concentrations. This sug- mechanism may be operative in obese women with PCOS gests that in these patients a dysregulation of the HPA axis remains, however, a matter for speculation. In fact, several may exist. The aforementioned data produced by Rodin and studies61,62 found a negative correlation between LH and colleagues42 suggest that in PCOS women an increased body weight in PCOS women, possibly depending on catabolism of cortisol may determine a compensatory hyper- reduced LH pulse amplitude and reduced LH response to activation of the HPA axis with the subsequent increased GnRH.62 Potential factors involved in the different LH pitui- androgen formation by the adrenal gland. According to an tary secretion between normal-weight and obese PCOS increased response of adrenal androgens68 and of ACTH and women may be insulin and neurotrasmitters such as b- cortisol41 to CRH administration the existence of a PCOS endorphin and catecholamines.59 In fact, a significant corre- women subset has been proposed. Mechanisms for the lation between insulin and LH levels has been found in PCOS exaggerated response of ACTH to hCRH in PCOS women women. Moreover, increased opioid tone and reduced dopa- remain unknown. However, according to the ability of minergic tone have also been described.59 Some authors have somatostatin analog treatment to abrogate ACTH hypere- also proposed that fat-associated factors, such as leptin, sponsiveness after CRH challenge69 some authors proposed a acting at hypothalamic or pituitary level, may dampen LH role for somatostatin in determining this dysregulation. secretion in the obese state.58 Obesity, particularly the abdominal phenotype, is also char- Clinical studies have repeatedly shown that obese PCOS acterized by a hyperactivity of the HPA axis (reviewed in women are characterized by significantly lower LH concen- Pasquali and Vicennati67). Two distinct alterations have been trations than their normal-weight counterparts61,62 and that, proposed. The first, which appears to be central in origin, is in very obese PCOS women, LH concentrations frequently characterized by altered ACTH pulsatile secretory dynamics, resemble the normal range.62 hyper-responsiveness of the HPA axis to different neuropep- Altogether, these data seem to indicate that increased LH tides and acute stress events, dysregulation of the noradre- secretion does not play a pivotal pathogenetic role in the nergic control of the CRH – ACTH system and, possibly, to majority of obese PCOS women. On the other hand, the distinct dietary factors. The other appears to be located in impact of obesity in LH pulse amplitude and frequency is the periphery, namely the visceral adipose tissue, which is difficult to define, due to the lack of studies on LH pulsatility characterized by elevated cortisol traffic and increased corti- secretion in PCOS women according to different body sol clearance, due to the influence of several distinct factors, weight and obesity phenotype. including alterations of the enzymes involved in cortisol metabolism. In addition, it is well known that P is able to interact with glucocorticoid receptors,50 therefore high P b-Endorphin. PCOS women are characterized by increased concentrations, such as those found during the luteal levels of plasma immunoreactive b-endorphin.5 In humans phase of the menstrual cycle, by competing with cortisol, b-endorphin administration increases insulin secretion from may reduce the effects of this hormone and further activate b cells.63 An inhibition of the opioid tone may induce a the HPA axis. This assumption is confirmed by the finding decreased hyperinsulinemia in PCOS women as a conse- that in obese women with irregular or absent ovulation, an quence of reduced insulin secretion and improved hepatic impairment in the cortisol activity is frequently detected.50 clearance.64 In addition, b-endorphin administration reduces In summary, in both PCOS and abdominal obese women LH release in normal women but not in PCOS women, several alterations of the HPA axis may be present. The high suggesting a condition of b-endorphin resistance in the prevalence of abdominal obesity in PCOS seems to suggest a PCOS.5 potential linkage between abdominal obesity and abnorm- Obesity by itself is characterized by an increased opioid alities of HPA axis in PCOS women. However, more detailed system activity.5 Moreover, infusion of physiological doses of studies are needed to discriminate the single contribution of b-endorphin has been found to induce a significant increase PCOS and obesity, respectively, in causing a disturbance of in insulin concentration in obese but not in normal-weight the HPA axis. subjects, suggesting b cell hypersensitivity to opioids in the obese state.65 In addition, both acute and chronic administration of opioid antagonists, such as naloxone and naltrex- Dietary factors one, are able to suppress both basal and glucose-stimulated Diet is a well-known factor playing a role in the regulation of insulin blood concentrations in obese women, particularly sex steroid metabolism. Several studies have demonstrated in those with the abdominal phenotype,66 but not in that high-lipid and low-fiber diet is related to an increase in normal-weight controls. An increased b-endorphin response androgen circulating levels.5 Moreover, as reported above, to acute CRH administration has also been found in women very high lipid intake has been found to decrease SHBG with abdominal obesity.67 However, there are no studies blood levels and increase free androgen index.5,70 In some investigating the net contribution of obesity to the opioid reports PCOS women were found to have a higher intake of tone and its ability to regulate insulin in PCOS women. saturated lipids and a lower intake of fibers when compared

International Journal of Obesity Obesity and the polycystic ovary syndrome A Gambineri et al 889 to control groups.71 Low-fiber and high-lipid intake has been reported that obese PCOS women may present inadequate considered one of the nutritional factors which favour insulin secretion to compensate for the peripheral insulin the onset and development of obesity in industrialized resistance state, suggesting a relative b cell dysfunction with countries.72 respect to that expected based on the degree of insulin Therefore, it can be speculated that a low-fiber – high-lipid resistance. However, regardless of alterations of insulin secre- diet may act negatively on sex steroid metabolism in selected tion, in a 10 y follow-up study we found that both fasting groups of PCOS women, by increasing androgen availability and glucose-stimulated insulin and C-peptide tended to and by favouring the development of obesity. further significantly increase in PCOS women, suggesting a worsened insulin resistant state with time.77 In the same study we also found that several women developed impaired Clinical features of obese women with PCOS glucose tolerance. Longitudinal data are therefore warranted Androgen abnormalities to investigate which factor, namely progressive insulin resis- Various studies evaluated the impact of obesity on the tance and=or subtle alterations of insulin secretion, may hyperandrogenic state in women with PCOS. They predict the well-documented susceptibility of obese PCOS uniformly demonstrate that obese PCOS women are char- women toward type 2 diabetes.4 Although PCOS per se may acterized by significantly lower SHBG plasma levels31,44,45 be associated with alterations of both lipid and lipoprotein and worsened hyperandrogenism45 in comparison with their metabolism, the presence of obesity usually leads to a more normal-weight counterparts. In addition, a negative correla- atherogenic lipoprotein pattern. A greater reduction of high- tion between body fat mass and circulating androgens has density lipoproteins (HDL)s44,73 together with a higher been reported in other studies.5,7 Moreover, it has been increase of both triglycerides44,67,73 and total cholesterol44 repeatedly described that a higher proportion of obese levels were in fact observed in obese with respect to the PCOS women complained of hirsutism and menstrual dis- normal-weight PCOS women. turbances than normal-weight women did.45 Therefore, there is consistent evidence that the increase of body weight may favour a worsened hyperandrogenic state in women with PCOS. Menses abnormalities and fertility PCOS is one of the most common causes of anovulation and endocrine infertility in women.78 Several studies have clearly demonstrated that menses abnormalities are more frequent Metabolic abnormalities in obese than normal-weight PCOS women.45,79 Moreover, PCOS women are characterized by a high prevalence of there is evidence that a reduced incidence of pregnancy and several metabolic abnormalities which are strongly influ- blunted responsiveness to pharmacological treatments to enced by the presence of obesity. Adequate confirmation induce ovulation may be more common in obese PCOS.78 on the genuine role of obesity in determining hyperinsuli- In a prospective study carried out among 158 anovulatory nemia and insulin resistance in women with PCOS derives women, the dose of clomiphene required to achieve ovula- from studies comparing groups of normal-weight and obese tion was positively correlated with body weight.80 Both PCOS women. Both fasting31,44,73,74 and glucose-stimu- insulin resistance and hyperinsulinemia, which parallel the lated31,75 insulin concentrations are in fact significantly increase of body fat, may be responsible for the alteration of higher in obese than in non-obese PCOS subgroups. Accord- both spontaneous and induced ovulation observed in the ingly, studies examining insulin sensitivity by using different obese PCOS women. Administration of insulin sensitizing methods such as the euglycemic hyperinsulinemic clamp agents, such as metformin81,82 and troglitazone83 was in fact technique,44,75 the frequent sample intravenous glucose test associated with improved menstrual cyclicity in women with (FSivGT)31,74 and the insulin test76 further demonstrated that PCOS. Moreover, a recent double-blind placebo-controlled obese PCOS women had significantly lower insulin sensitiv- collaborative study, performed in a large cohort of PCOS ity than their non-obese PCOS counterparts and, therefore, a women,84 demonstrated that short-term metformin treat- more severe insulin-resistant state. The percentage of women ment increased both spontaneous and particularly low affected by PCOS and obesity presenting glucose intolerance dose (50 mg daily for 5 days) clomiphene-induced ovulation is rather high, ranging from 20 to 49%,15 therefore substan- rate. It has also been found that, compared to normal- tially above the prevalence rates reported in premenopausal weight, obese PCOS women may have lower ovulatory women in population-based studies. On the contrary, glu- response to pulsatile GnRH analog administration.85 Accord- cose intolerance in normal-weight PCOS women is uncom- ingly, the pregnancy rate after a low-dose human menopau- mon.15 Altogether, this may indicate that obesity per se plays sal gonadotropin (hMG) or pure FSH administration may be an important role in altering the insulin – glucose system in significantly lower in obese than in normal-weight PCOS PCOS. In addition, several recent studies identified some women.86 Finally, in recent studies on PCOS women con- defects of insulin secretion in obese women with ceiving after in vitro fertilization or intracytoplasmatic sperm PCOS.31,74 Using the FSivGT, Dunaif and colleagues74 injection, it was observed that those with obesity had higher

International Journal of Obesity Obesity and the polycystic ovary syndrome A Gambineri et al 890 gonadotrophin requirement during stimulation,87 fewer Treatment of women with obesity and PCOS oocytes, a higher abortion rate and lower live-birth rate Effect of weight loss than their non-obese counterpart.88 In conclusion, a There is long-standing clinical evidence concerning the decreased efficiency of the different treatments for ovulation efficacy of weight loss upon clinical and endocrinological and fertility induction may be expected in obese PCOS features of obese women presenting PCOS. However, the women. The presence of hyperinsulinemia is probably the effects of weight loss on the clinical course of women major factor responsible for this undesirable condition. with obesity and PCOS have not been as deeply investigated as the pharmacological management of the syndrome. Weight loss improves menses abnormalities and, most importantly, both ovulation and fertility rate.7 The The impact of body fat distribution reduction of T, androstenedione (A) and dehydroepian- It is well documented that women with PCOS have a high drosterone-sulphate (DHEAS) levels and the increase of prevalence of abdominal body fat distribution, even if they SHBG concentrations appear to be responsible for the are normal-weight.89 The impact of abdominal obesity on amelioration of the signs and symptoms reported after PCOS may be greater than expected, since this phenotype weight loss in obese PCOS women. Moreover, there are is associated with a more pronounced hyperandrogenism indications that weight loss may decrease LH pulse ampli- and insulin resistance than the peripheral one. We have tude which, in turn, can be followed by reduced androgen repeatedly demonstrated that the androgen profile and insu- production.91 The key factor responsible for these effects is lin basal levels as well as the insulin response to a glucose the reduction of the insulin level which is obviously load are significantly higher in the subgroup with abdominal associated with an improvement of the insulin resistant body fat distribution than in the group with the peripheral state. A concomitant decrease in T and insulin concentra- type, regardless of BMI.46,47 This has been confirmed in tions (both basal and glucose-stimulated) has been studies using dual-energy X-ray absorptiometry (DEXA) to described regardless of body weight variations.92 Diet- define different obesity phenotypes.90 Holte et al91 found a induced reduction of insulin levels has been demonstrated significant association between abdominal fat mass and to decrease the P450c17a enzyme activity and conse- insulin resistance evaluated by the euglycemic hyperinsuli- quently the ovarian androgen production.93 In addition, nemic clamp technique. They also found a highly significant reduction of leptin associated with the weight loss may correlation between FFA concentrations and insulin resis- lead to a deactivation of the neuroendocrine control of tance, which supports the concept that an increase of FFA ovarian steroid secretion.94 The best therapeutic strategy flux from the highly lypolytic abdominal fat to the liver and for favouring weight loss in obese PCOS women has not muscles may represent the most important link between been investigated. However, conventional hypoenergetic abdominal obesity and the insulin resistance state.91 More- diets have proved their efficacy both in reducing hyper- over, this subgroup of PCOS women may have a more androgenism and improving fertility.95 There are no stu- unfavorable lipid profile, namely higher triglyceride and dies investigating the effects of different regimens. On the very-low-density lipoprotein (VLDL) and lower HDL choles- other hand, in one study a moderate weight loss of just terol concentrations.47 In addition, PCOS women with the over 5% was found96 to achieve the same effects described abdominal phenotype present a higher prevalence of menses after more sustained weight loss.94 In addition, long-term abnormalities and acanthosis nigricans (a cutaneous marker trials investigating the effects of weight maintenance over of insulin resistance) and a tendency towards worsened several years are still needed. As discussed in the following hirsutism.47 As discussed above, abdominal obesity is asso- paragraph, whether hypocaloric dieting combined with ciated with profound alterations of both production and chronic treatment with insulin sensitizers may be more metabolic clearance rates of major androgens and reduced effective than diet alone is still under debate. However, SHBG blood levels. In abdominally obese PCOS women based on our results,94 we can conclude that this combi- androgens could, in turn, play a role in regulating tissue nation may further improve the effects of diet on body metabolism. In fact, at the level of visceral depots, T stimu- weight loss, and on the reduction of visceral fat depots, lates lipolysis and, therefore, increases FFA efflux.50 In addi- and may produce a greater amelioration of insulin sensi- tion, at the level of the muscle, T modifies the histological tivity and hyperandrogenism and menses abnormalities. structure by increasing type II, less insulin-sensitive fibers. To summarize, weight loss in women with obesity and These androgen-dependent mechanisms may have a further PCOS not only reduces total and visceral fat, but also important impact on the insulin resistance state. restores normal menstrual cycles and improves the fertility In summary, in women with PCOS, abdominal obesity per rate in a large proportion of affected women, by reducing se may play a key role in determining both altered androgen androgen and insulin concentrations and improving insu- metabolism and insulin resistance in a vicious circle manner. lin sensitivity. Notably, the effects of dietary-induced This may be of importance in phenotyping PCOS and in the weight loss on androgens seem to be specific to obese therapeutic strategy aimed at reducing both hyperinsulinism hyperandrogenic women, since they have not been and hyperandrogenism. reported in non-PCOS obese women.97

International Journal of Obesity Obesity and the polycystic ovary syndrome A Gambineri et al 891 Insulin-lowering drugs trations were observed after metformin administration in As concluded above, diet itself may positively effect hormo- PCOS abdominally obese women when compared to pla- nal and metabolic parameters in PCOS obese women. How- cebo. In PCOS patients these changes were associated with a ever, insulin suppression obtained after diazoxide significant improvement of hirsutism and menses abnorm- administration has been shown to reduce T and to increase alities. These findings led us to conclude that hyperinsuline- SHBG concentrations in obese and PCOS hyperandrogenic mia and abdominal obesity may have complementary effects women without affecting body weight.98 The same treat- in the pathogenesis of PCOS. ment has been described to be ineffective in normal-weight There are few studies on the effects of thiazolidinediones controls.99 Therefore, drug-induced reduction of insulin in PCOS. Troglitazone (400 mg daily) has been shown to levels has been proposed as the primary goal to be achieved. improve total body insulin sensitivity in obese PCOS We have commercially available insulin-sensitizers, such as women, resulting in lower circulating insulin levels. A sub- metformin, a drug belonging to the class of biguanides100 stantial improvement of the PCOS-derived metabolic and and thiazolidinediones, which are selective ligands for hormonal alterations was observed after administration of PPARg, a member of the nuclear receptor superfamily of this drug, as indicated by a decline of T and of triglycerides ligand-activated transcription factors,101 and drugs under and plasminogen activator inhibitor type I, which are risk investigation, such as D-chiro-inositol, a component of the factors for the development of cardiovascular diseases.83,106 signal transduction system of insulin.24,102 The efficacy of In addition, short-term troglitazone administration has been these compounds in ameliorating hyperinsulinemia and found to improve spontaneous ovulation in anovulatory insulin resistance and hyperandrogenism in women with PCOS women.7 There are no clinical studies using the new PCOS is briefly summarized in the following paragraph. thiazolidinediones, rosiglitazone and pioglitazone in PCOS women. Clinical studies with insulin lowering drugs. Velasquez Among other insulin-sensitizing agents, the potential use et al first demonstrated that metformin administration in of D-chiro-inositol in PCOS treatment is currently under obese PCOS women was not only able to significantly investigation. Inositolglycans have been described as med- improve insulin levels, but also to decrease LH and T con- iating insulin action on thecal steroidogenesis.24 Taking into centrations, regardless of changes in body weight, with a consideration these in vitro findings, Nestler et al proposed D- significant improvement of menses abnormalities in most chiro-inositol therapy for PCOS women, demonstrating in a patients.82 The finding of the beneficial effect of long-term placebo-controlled trial that this drug is able to decrease metformin treatment on fertility has been confirmed by insulin secretion during the oral glucose tolerance test and many other studies, as recently reviewed by Oberfield.103 to concomitantly increase plasma SHBG. These hormonal Short-term metformin administration (1500 mg=daily for 1 changes have been described as being accompanied by a month) has been shown to reduce insulin levels and 17a- significant restoration of spontaneous ovulation.107 hydroxyprogesterone and LH response to leuprolide.8 Higher In conclusion, the data from the literature strongly sup- plasma insulin and lower serum A levels associated with less port the hypothesis that in women with obesity and PCOS, severe menstrual abnormalities before treatment seem to be improvement of hyperinsulinemia can be associated with predictive of a beneficial outcome of metformin treat- various clinical benefits, including reduced hyperandrogen- ment.104 An improvement of the ovulation rate in obese ism and related clinical features and improved menses cycli- PCOS women has also been described after short-term use of city and ovulation. In addition, the use of insulin-sensitizers metformin. As reported above, recent data indicate that could be viewed as a potential strategy to control the meta- administration of this drug may also remarkably increase bolic syndrome and prevent the increased susceptibility to clomiphene-induced ovulation in comparison to pla- develop diabetes and cardiovascular diseases later in life. On cebo.83,84 However, there are some studies105 finding no the other hand, this is an unanswered question that needs to improvement of insulin resistance and hyperandrogenism be verified by appropriate long-term interventional studies. during metformin administration on PCOS. The differences in results between studies might be related to the methods used to evaluate insulin resistance, to the criteria used for Other drugs recruitment (entity of obesity and of insulin resistance), to Antiandrogens. As previously reported, several studies the number of subjects included in the study and to the have demonstrated that antiandrogens, as well as reducing duration of treatment. Recently, we performed a 6 month androgen levels, may significantly improve insulin resistance double-blind controlled study to investigate the effect of a and hyperinsulinemia in either obese and non-obese PCOS combined metformin administration (500 mg twice daily) women. These effects have been observed regardless of the and hypoenergetic diet on insulin, androgens and fat dis- type of drug used, the results observed being substantially tribution in a group of abdominally obese women with and similar for spironolactone,55 flutamide,54,108 finasteride54,55 without PCOS.94 A greater reduction of body weight and or GnRH agonists.108 On the other hand, there are no studies abdominal fat, particularly the visceral depots, and a more investigating the effect of pure antiandrogens on body consistent decrease of serum insulin, T, and leptin concen- compartments and fat distribution in these women. One

International Journal of Obesity Obesity and the polycystic ovary syndrome A Gambineri et al 892 study109 using a GnRH agonist has shown an increment in gens, cyproterone acetate is almost as effective as GnRH abdominal fat and total visceral adipose volume in a cohort agonist at suppressing serum LH and T, and the clinical of hyperandrogenic anovulatory women. However, these efficacy of the two treatments are equivalent.114 In addition, results cannot be translated to pure antiandrogens because by investigating the long-term effect of oral contraceptive a GnRH agonist induces a decrease in both estrogen and therapy on metabolism and body composition in a group of androgen secretion. In addition, no studies have investigated PCOS women we found a significant reduction of waist the combined effect of antiandrogens and hypoenergetic circumference and of WHR, as well as of basal insulin dieting with or without insulin sensitizers. Preliminary data levels and an improvement of glucose tolerance in some from our group, obtained in a 6 month study on a group of subjects.77 These favorable effects were not, however, obese PCOS women, seem to be consistent with a beneficial observed in a group of non-treated women, who had wor- effect of this combination in selectively reducing visceral fat sened fasting and glucose-stimulated insulin levels. (unpublished data). Although controversy still exists concerning the effect of oral contraceptive preparations on glucose metabolism and Oral contraceptives. Over the years oral contraceptives insulin secretion and action in non-PCOS women, the results have been widely used in women with PCOS. The actions of this study indicate a potential benefit of long-term estro- of these compounds involve several mechanisms. The pro- progestagen compounds in body composition and the gestagen component decreases the frequency of GnRH pulses glucose-insulin system at least in PCOS women. and LH secretion, thus reducing ovarian estrogen and androgen production, while estrogen induces P receptors in the Antiobesity drugs. In spite of the potential benefits of the hypothalamus and also increases SHBG concentration.110 use of orlistat or sibutramine, the drugs currently available Many studies have documented a reduction in T levels and for treating obesity, there are no trials investigating their the best results are described in subjects with hyperandro- effects in obese PCOS women. genic states such as PCOS patients. Moreover, hirsutism may improve during long-term oral contraceptive treatment, but usually reverses with discontinuation of the therapy. The Summary and conclusions most clinically efficacious approach using oral contracep- In this review we have analyzed the clinical characteristics tives in PCOS women can be obtained combining estrogen and physiopathological aspects of obesity-associated PCOS. with cyproterone acetate, which has both progestagen and Obese women with PCOS seem to be characterized by a anti-androgen activity and also induces hepatic metabolism different hormonal environment from that of normal- and increases T clearance.111 – 113 In combination with estro- weight affected women. The main differences are more

Figure 1 Mechanisms by which obesity may determine the obesity – PCOS phenotype.

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