Journal of Pediatric Surgery (2010) 45, 2074–2086

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Review articles What is new in and —a critical review on the testicular dysgenesis hypothesis☆ Jorgen Thorup a,⁎, Robert McLachlan b, Dina Cortes c,d, Tamara R. Nation f, Adam Balic f, Bridget R. Southwell f, John M. Hutson e,f,g aDepartment of Pediatric Surgery, Faculty of Health Science, University of Copenhagen, Rigshospitalet, DK-2100 Copenhagen, Denmark bPrince Henrys Institute of Medical Research, Monash Medical Centre, 3168 Clayton, Australia cSection of Pediatric Endocrinology, Hvidovre Hospital, 2650 Copenhagen, Denmark dFaculty of Health Science, University of Copenhagen, DK-2100 Copenhagen, Denmark eDepartment of Pediatric , Royal Children's Hospital, VIC 3052 Melbourne, Australia fDouglas Stephens Surgical Research Laboratory, Murdoch Children's Research Institute, VIC 3052 Melbourne, Australia gDepartment of Paediatrics, University of Melbourne, VIC 3010 Australia

Received 15 February 2010; revised 18 July 2010; accepted 19 July 2010

Key words: Abstract It has been hypothesized that poor , testis cancer, undescended testis, and Cryptorchidism; hypospadias are symptoms of one underlying entity—the testicular dysgenesis syndrome—leading to Hypospadias; increasing male fertility impairment. Though has increased in many Western countries Fertility; during the past 40 years, hypospadias rates have not changed with certainty over the same period. Also, Testicular cancer; recent studies demonstrate that sperm output may have declined in certain areas of Europe but is Epidemiology probably not declining across the globe as indicated by American studies. However, at the same time, there is increasing recognition of related to obesity and smoking. There is no certain evidence that the rates of undescended testes have been increasing with time during the last 50 years. In more than 95% of the cases, hypospadias is not associated with cryptorchidism, suggesting major differences in pathogenesis. Placental abnormality may occasionally cause both cryptorchidism and hypospadias, as it is also the case in many other congenital malformations. The findings of early orchidopexy lowering the risk of both infertility and testicular cancer suggest that the abnormal location exposes the cryptorchid testis to infertility and malignant transformation, rather than there being a primary abnormality. Statistically, 5% of testicular cancers only are caused by cryptorchidism. These data point to the complexity of pathogenic and epidemiologic features of each component and the difficulties in ascribing them to a single unifying process, such as testicular dysgenesis syndrome, particularly when so little is known of the actual mechanisms of disease. © 2010 Elsevier Inc. All rights reserved.

☆ The rates of hypospadias, cryptorchidism, and testis This present review is based on lectures presented at the World cancer are thought to be increasing, whereas sperm Federation of Associations of Pediatric Surgeons' session at The International Surgical Week in Adelaide, Australia 2009. concentrations are decreasing [1]. Several epidemiologic ⁎ Corresponding author. Tel.: +45 3545 4868; fax: +45 3545 3888. studies have shown that these conditions are associated with E-mail address: [email protected] (J. Thorup). each other. Skakkebaek et al [2] have hypothesized that poor

0022-3468/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.jpedsurg.2010.07.030 Cryptorchidism and hypospadias 2075 semen quality, testis cancer, undescended testis, and hypospadias is a continuum depending on when during the hypospadias are symptoms of one underlying entity—the embryonic period the fusion fails. so-called testicular dysgenesis syndrome (TDS). They have The only hitherto well-established risk factor for suggested that an imbalance between estrogens and andro- hypospadias, when corrected for gestational age, is low gens during fetal life may be crucial. Initially, the estrogen birth weight [15-19]. In 16 of 18 monozygotic twins hypothesis argued that increasing of reproductive abnormal- discordant for hypospadias, the twin with the lowest birth ities in human males may be related to increased estrogen weight had hypospadias [15,20]. Because low birth weight exposure in utero [3]. This hypothesis has been expanded to and small-for- gestational age are associated with suboptimal include endocrine disruptors, which include environmental first trimester growth, the association with hypospadias may toxins that can disrupt the hormonal balance of the fetus and be related to early placental malfunction [21]. Accordingly, thereby disturb sexual differentiation either by an estrogenic hypospadias has been correlated with low weight of the or an antiandrogenic effect [4]. Data also indicate that placenta [15,22,23]. Abnormalities of the fetal-placental- estrogens can induce cryptorchidism and hypospadias by maternal interaction may also explain the finding of an suppressing androgen production or action. In addition, association with dystocia, as women who gave birth to boys estrogen can induce cryptorchidism by suppression of with hypospadias had a higher rate of weak contractions insulin-like factor-3 [1,5]. Various environmental chemicals during birth, induced deliveries, and caesarean sections [24]. are able to alter endogenous levels of androgens (certain Hypospadias has also been shown to be associated with phthalates) and estrogens (polychlorinated biphenyls, poly- preeclampsia later during pregnancy [18]. Interestingly, there halogenated hydrocarbons) [1,5,6], but so far, few studies is a higher incidence of hypospadias with increasing have shown any clinical impact [7]. Endocrine disruptors, maternal age, what may be a direct consequence of the age such as phthalates and bisphenol-A, have been manufactured or other factors, such as a higher frequency of in vitro for more than 50 years and are widely used in plastic bottles, fertilization in older women [25]. vinyl floors, food wraps, cosmetics, medical products, and toys, so if they had an effect, it should be seen in the 1.2. Genetics epidemiologic data. However, the data do not support this. The hypothesis of possible environmental estrogenic or Genetic mechanisms are indeed involved in the patho- antiandrogenic effect of reproductive abnormalities in human genesis of hypospadias. Familial clustering is seen in 4% to males is mainly based on animal studies [8-13]. 25% of cases [15,16,23,26-30]. The more severe the The term “syndrome” derives from its Greek roots and malformation of the index patient, the higher the recurrence means literally “run together.” as the features of the TDS risk for the next male sibling, ranging between 9% and 17% should do. However, as will be discussed in the following, [15-17,23,26]. The distribution of phenotype in sporadic and substantial data related to pathophysiology as well as familial cases differs. Minor hypospadias is more common in epidemiology do not concur TDS hypothesis. Except for a familial than sporadic cases, whereas severe variants are few individuals with abnormal 45X/46,XY karyotype and more commonly sporadic [15]. other disorders of sexual development, few patients display all features of the “syndrome,” but rather 1 or 2 features for which alternative etiologies and associations can be 1.3. Epidemiology proposed. In a syndrome, a particular set of multiple anomalies occurs repeatedly in a consistent pattern. The A study by Paulozzi [31] reviewed data from 29 complexity of pathogenic and epidemiologic features of each registries on 4 million births per year around the world and component of TDS pathology and the difficulties in ascribing revealed wide intercountry variation in rates of hypospa- them to a single unifying process indicate that this is likely dias. Given differences in registry methods, genetic varia- not a syndrome. In this review, we critically evaluate the tion, and other factors, the rates themselves were not present knowledge about the etiology and epidemiology of directly comparable; however, they showed changes within hypospadias and cryptorchidism, and speculate on alterna- systems in recent decades. The data suggested an increase tive ways to look at the conditions. in reported rates of hypospadias during the 1970s and 1980s in 2 US systems, Scandinavia, and Japan. Among other nations, increases were only seen in one Italian system and in the Israeli system. The absence of an 1. Hypospadias increase was perhaps most notable in Canada, where the society is similar to that of the United States. However, the 1.1. Pathogenesis data collected from the US Birth Defects Monitoring Program (BDMP) were not random and did not accurately Hypospadias is caused by failure of fusion of the urethral represent the US population well in terms of geography. folds, endodermal differentiation, and ectodermal ingrowth Among all systems showing an increase, rates tended to in gestational weeks 8 to 20 [14,15]. The severity of level off after 1985. We reviewed more detailed studies on 2076 J. Thorup et al.

Table 1 The incidence rates of hypospadias in Denmark according to 4 different studies Reference Period Method Total no. Incidence of hypospadias (%) of boys Sorensen [32] 1910-1945 Patient files + follow-up 27 613 0.33 (at birth) Weidner et al [19] 1983-1992 National register 330 000 0.40 (discharge diagnosis) Boisen et al [33] 1997-2004 Prospective clinical investigation 1072 0.75 (at birth) Breddam et al [22] 2002-2006 Patient files + follow-up 1087 0.83 (at birth); 0.92 (4-y follow-up investigated by a pediatrician); 0.64% (4-y follow-up investigated by a surgeon)

the incidence of hypospadias in Denmark (Table 1) [22]. OR of hypospadias with other congenital abnormalities, such The trend was quite clear. The incidence rate of hypo- as imperforate anus, is much higher (Table 2) [36]. spadias diagnosed at birth was increased during a 60-year period when comparing the data collected in the 1940s by 1.4. Fertility aspects Sorensen [32] and the data collected in the first decade of the 21st century by Boisen et al [33] and Breddam et al [22]. In a recent study, Asklund et al [37] found that the semen The incidence rates of hypospadias in 4 Danish published quality of men with operated isolated hypospadias did not studies were 0.33% in 1953 [32], 0.4% in 1999 [19], 0.75% differ from controls, but that semen quality was reduced in in 2005 [33], and 0.64% to 0.83% in 2008 [22] (Table 1). men with hypospadias and additional genital disorders, With our detailed knowledge of the Danish studies, we predominately cryptorchidism. In 42% of these patients, a had no reason to doubt the validity of the figures (Table 1). sperm density less than 20 million/mL was found. In another The only possible bias seems to be a possible changing of study by Bracka [38], 25% of 41 hypospadias patients diagnostic criteria of hypospadias at inclusion. A recent including 26 patients also with cryptorchidism had a sperm study from 2009 had shown hypospadias rates have not density less than 20 million/mL. However, in both studies, changed in New York State from 1992 to 2005 [34].Ina hypospadias patients with treated cryptorchidism included a recent review of incidence studies on hypospadias, Fisch mixture of bilateral and unilateral cases. For comparison, in et al [35] demonstrated that the rising rates described collected series of patients with previous treated isolated during the 1960s to 1980s trailed off by roughly 1985, at cryptorchidism, 79% of bilateral and 31% of unilateral cases which time there was no rise, or an actual decline. had a sperm density less than 20 million/mL [39]. Consistent with the TDS concept, hypospadias is indeed Even among some authors strongly advocating for the associated with cryptorchidism. In a Swedish study on clinical impact of the testicular dysgenesis hypothesis, it hypospadias, 6% had cryptorchidism on one or both sides seems now evident that among men with isolated hypospa- [15]. However, although the odds ratio (OR) of hypospadias dias and impaired spermatogenesis, only a fraction of cases cases also having cryptorchidism equals approximately 5, the are linked to the TDS [40].

Table 2 The OR of the association of hypospadias with other 2. Cryptorchidism malformations [36] Characteristics Cases Controls Crude CL 2.1. Pathogenesis (n = 2382) (n = 235542) OR Small for 378 18948 2.16 1.9-2.4 The etiology and epidemiology of cryptorchidism differs gestational age significantly from that of hypospadias, thereby challenging Cleft-palate 6 107 5.56 2.4-12.6 the holistic TDS concept. (isolated) There is considerable controversy regarding the etiology Cleft + lip + evt. 12 394 3.02 1.7-5.4 of undescended testis. However, it is often asserted that palate hypogonadism accounts for some of these cases [41,42]. Oesophageal 3 43 6.91 2.1-22.3 Certainly, the etiology is multifactorial, since disrupted atresia endocrine regulation and several gene defects may cause Imperforate anus 8 40 19.84 9.3-42.4 cryptorchidism [43]. Diaphragmatic 3 65 4.57 1.4-14.5 hernia The first phase of testicular descent occurs between weeks Omphalocele/cord 3 39 7.62 2.4-24.7 10 and 15 of human gestation [44]. This is independent of hernia androgen, as the process occurs normally in animal models and humans with complete androgen insensitivity [45] and is Cryptorchidism and hypospadias 2077 controlled by Müllerian inhibiting substance (also known as There is much clinical evidence that reduced androgen anti-Müllerian hormone) [41,45] and insulin-like hormone 3 action is associated with undescended testes [68-70].Testos- (INSL3) [46]. The primary hormone-regulating transabdom- terone deficiency in humans may result from decreased gonadal inal descent is thought to be INSL3 [46]. Insulin-like function or problems with the hypothalamic-pituitary axis. hormone 3, also known as relaxin-like factor, is a member of Placental human chorionic gonadotrophin stimulates androgen the insulin-like hormone superfamily [47]. It is secreted by secretion in early fetal development. Androgen secretion is the Leydig cells shortly after the onset of testicular driven by pituitary luteinizing hormone (LH) from 20 weeks of development and controls the swelling reaction of the gestation. Serum levels are highest at 12 to 16 gubernaculum [48]. Targeted deletion of the INSL3 gene weeks gestation and decrease after week 17 to 28 weeks in mice causes bilateral cryptorchidism [49], but its role in [69,70]. Consequently, serum testosterone is highest in the early human testicular maldescent is uncertain [50]. One study stages of testicular descent. There is a postnatal surge in found only 1.9% of cases of cryptorchidism to be caused by testosterone at 3 to 6 months of age, which is reduced in some INSL3 gene mutations [51]. Similarly, mutations of the cryptorchid cases [71]. INSL3 receptor (LGR8) are uncommon [52]. A case-controlled study that looked at 199 mothers of These observations are in accordance with the finding that cryptorchid males vs 199 mothers of noncryptorchid males with intra-abdominal undescended testes comprise only 5% of normally descended testes found that maternal third trimester operations for undescended testes [53]. Furthermore, only blood samples screened for estradiol and estriol were higher in 42% to 61% of the intra-abdominal testes are located at the control than cryptorchid cases [72]. Estriol is synthesized in the iliac vessels or higher, remote from the internal ring (high placenta and requires the fetal substrate, dehydroepiandroster- intra-abdominal) [54-57], which may indicate a true failure one. Estriol, therefore, can be used to evaluate fetal-placental of transabdominal descent. The fact that transabdominal circulation. The source of estrogens during pregnancy is the descent occurs between 10 and 15 weeks of gestation, during placenta, which aromatizes prohormones produced by the fetus. the same critical period as penile development, may explain Dehydroepiandrosterone is also a precursor to androgen. why hypospadias is seen in 4.3% of boys with intra- Therefore, abnormal placental-fetal circulation has been abdominal undescended testes compared with 1.4% to 1.6% implicated as a contributing factor to cryptorchidism and in unselected cryptorchid boys [58-60]. In this respect, it has maybe viewed as critical for hormone regulation. to be emphasized that more than 98% of cryptorchid boys Cryptorchidism is associated with other congenital abnor- have no hypospadias. malities in less than 20% of cases, but when present, then most The second or inguinoscrotal phase of descent of the testis often related to abnormalities of the midline and caudal occurs between approximately 26 to 40 weeks of gestation developmental fields [39]. The defects may be asymmetrical [44]. After completion of the first phase of descent at about and the full expression not seen until later in fetal life [39,73]. 15 weeks of gestation, there is a gap of approximately 10 Association between cryptorchidism and abnormal caudal weeks before the onset of the second phase, which may be development is relatively more common than that of isolated related to development of the central nervous system. During cryptorchidism and hypospadias. The close relationship the second phase, the testis migrates through the inguinal between cryptorchidism, imperforate anus, and abnormal canal and across the pubic region to the . The testis caudal development had been described in detail by Cortes et and epididymis remain within a diverticulum of the al [74]. In a series of 34 cryptorchid boys younger than 3 years, peritoneum that elongates within the elongating gubernacu- caudal abnormalities, malformations, and dysplasias of the lum [61]. In humans, the distal end of the gubernaculum kidneys, the ureters, and the spine from T10 to S5 were the remains bulky until after descent is complete. In both humans predominant abnormalities in 18% of these cryptorchid and rodents, there is a significant inguinoscrotal phase. The individuals [75]. Also, autopsy data show coexisting urogenital gubernaculum in humans is approximately 1 cm in diameter, abnormalities in 31% of cryptorchid boys and coexisting and the distance that it needs to migrate it is approximately 4 urological abnormalities in 14% of cryptorchid adults [76].The to 5 cm [61,62]. cryptorchidism was on the same side as the urological Recent evidence from laboratory studies suggests that the abnormalities in 93% of cryptorchid boys [39]. The position gubernaculum may be growing out of the abdominal wall in and histology of undescended testes were independent of a the a manner very similar to an embryonic limb bud [63], abnormalities encompassed by the association [39,75,77]. possibly using the same genetic regulatory factors as the Abnormal placental-fetal circulation implicated as a cause of pharyngeal arches and genital tubercle [64]. The guberna- the spectrum of so-called human caudal malformation culum growing out of the abdominal wall might also be sequences has been hypothesized many years ago [78]. under similar regulatory control [65], as Hoxa10- and Hoxa11-knockout strains of mice were cryptorchid [66,67]. 2.2. Genetics Fgf-10 and Hoxa10 are expressed in the inguinal region immediately distal to the gubernaculum. Mutations in these Generally, more than 80% of undescended testes are not genes may explain many of the genetic causes of related to associated malformations or diseases [39]. Familial cryptorchidism in boys. inheritance is well known. In a recent population-based study 2078 J. Thorup et al. of 1 024 500 boys, concordance rates of cryptorchidism in in 2.6% of twins compared with 2.4% in singletons, despite the groups were as follows: boys with no relation, 3.2% that the frequency of a birth weight below 2500 g was 51% in (95% confidence interval, 2.7%-3.6%); paternal half- twins and 4.9% in singletons. Hence, the special hormonal brothers, 3.4% (2.3%-4.7%); maternal half-brothers, 6.0% influence of the prenatal twins maybe related to the greater (4.5%-7.7%); full brothers, 8.8% (8.3%-9.8%); dizygotic and more competent placenta possibly leading to a lower risk twin brothers, 24.1% (16.0%-33.6%); and monozygotic twin of cryptorchidism. Berkowitz et al [87] and Weidner et al brothers, 27.3% (15.5%-41.2%) [79]. Geographic variation [19] also found a low risk of cryptorchidism in twins when in prevalence of cryptorchidism in 2 Nordic countries with corrected for birth weight and prematurity. Equally, Biggs et similar health care systems but with populations of different al [90] found an elevated risk of cryptorchidism in cases with ethnic origin supports the proposal that genetic factors are placental abnormalities. involved in some cases [80]. Boisen et al [80] found a 4-fold To facilitate comparison, several large series have higher incidence of cryptorchidism in Danish people addressed the incidence of congenital isolated cryptorchi- compared with Finnish people. dism in newborns more than 2500 g in weight. Including only those males born with a birth weight more than 2500 g, 2.3. Epidemiology the incidence of cryptorchidism in studies during the last 50 years has been noted to be 1.8% to 8.5% and is bilateral in Generally, it is difficult to compare the frequency of about 30% of the cases (Table 3) [80,85-88,91-96]. Over the cryptorchidism in different publications [81,82], as the years, the prevalence of cryptorchidism in full-term males definition of cryptorchidism varies. One can readily define seems to be quite stable and actually with only small an undescended testis as one not being in the scrotum [39]. differences between geographical areas. However, at first However, some testes are not in the scrotum when the glance, the study by Boisen et al [80] showed a clearly examination starts but can be brought down to some degree. conflicting result. They identified cryptorchidism in 8.5% of Some authors even include high scrotal testes (that can be full-term newborn Danish males with a birth weight of more manipulated to the bottom of the scrotum but immediately than 2500 g but, in doing so, included 6.5% high scrotal return to a higher, but still scrotal position), into the group testes that could be manipulated to the bottom of the scrotum with congenital undescended testes [80]. but immediately returned to a higher, but still scrotal Retractile testes are those that move spontaneously out of position. They introduced new terminology such as “severe” the scrotum on a regular basis and/or on initial examination cryptorchidism, which then has the same prevalence in those but will return, either spontaneously or with manipulation, to males born with a birth weight of more than 2500 g, as seen a dependent scrotal position and remain there for a finite but in other Danish studies—namely ∼2%. Hence, they seem to ill-defined period. Testicular ascent and acquired cryptorchi- indicate a mild form of cryptorchidism including scrotal dism pertain to testes that are documented to be in a scrotal testes that they identify as abnormal. We are not convinced position at least once after birth but subsequently will not that the so-called high scrotal testes have been included in remain in a satisfactory scrotal position [83-85]. previous Danish prevalence studies on newborns. Many The estimation of the position of the undescended testis testes return to a higher scrotal position when palpated, will always be partly subjective, since it is on a mesentery especially in a cold environment. Thus, one cannot conclude within the tunica vaginalis. The frequency of undescended that the prevalence of these proposed abnormal scrotal testes testes in a population is dependent on birth weight. has changed over time. We regard it as much more important Premature boys have a significantly increased risk of that Cortes et al [91] identified a 1.9% prevalence of cryptorchidism [80,86-88], possibly because of the early undescended testes in Danish newborn males with birth delivery itself. However, in these preterm boys, the testes weight of more than 2500 g in 2007 vs 1.8% in the study of usually descent postnatally, and most will not have Buemann et al [88] in 1961. Thus, a true slight increase cryptorchidism by the time of expected birth [87]. cannot be excluded. Also, the study by Preiksa et al [96] from In the literature, the incidence of undescended testes at 2005 showing a prevalence of 4.6% includes the high scrotal birth for premature and/or birth-weight (b2500 g) infants testes that could be manipulated to the bottom of the scrotum varies from 1.1% to 45.3% (most often around 20%-30%) but immediately returned to a higher position in the group and bilateral presentation in 50% to 75% [83]. Low birth with cryptorchidism. Therefore, the overall prevalence of weight is a well-known association with cryptorchidism and cryptorchidism in males born with a birth weight of more may be related to impaired placental function. Testicular than 2500 g varies between 1.8% and 4.1% depending on descent is at least partially dependent on fetal testicular primarily geographical genetics, study design, and differ- testosterone, which, in turn, is initiated and maintained by ences in definitions and classifications, and exclusion of human chorionic gonadotrophin produced by the placenta “scrotal undescended testes.” Importantly, these figures [89,90]. appear not to have increased over time. Though the risk of cryptorchidism generally is elevated in Of full-term males noted to have cryptorchidism at birth, low birth weight, this was not the case in twins studied by spontaneous descent is reported to occur in some patients Cortes et al [91]. They found a frequency of cryptorchidism usually by age 1 to 3 months, with descent at 6 to 9 months Cryptorchidism and hypospadias 2079

Table 3 Incidence of congenital undescended testes in newborn boys with a birth weight more than 2500 g References Country Year of Total n Prevalence Bilateral Assessment at publication at birth (%) (%) follow-up (1-4 y), prevalence (%) Scorer [92] UK 1964 3612 2.7 11 – Villumsen and Zachau-Christiansen [85], Denmark 1966 4500 1.8 29 0.7 Buemann et al [88] Hirasing et al [93] Netherlands 1982 1781 2.0 –– John Radciffe Hospital Cryptorchidism UK 1992 7400 4.1 34 1.6 Study Group [86] Berkowitz et al [87] US 1993 6935 2.2 – 1.0 Thong et al [94] Malaysia 1998 882 2.4 29 – Ghirri et al [95] Italy 2002 9343 3.4 – 1.5 Boisen et al [80] Finland 2004 1426 2.1 –– Boisen et al [80] Denmark 2004 1005 8.5 –– Preiksa et al [96] Lithuania 2005 1135 4.6 31 – Cortes et al [91] Denmark 2008 1088 2.1 15 1.6

occurring rarely, so that when followed up at the age of 1 There are few studies following undescended testes year, the prevalence of cryptorchidism is generally lower nonoperatively through childhood and puberty (Fig. 1) [99- (Table 3). Spontaneous postnatal descent in preterm and full- 101]. There is no doubt that a late spontaneous descent term boys occurs more often in bilateral than in unilateral occurs in some cases, probably mainly in retractile testes. cases, and more often in smaller boys at birth. This is in With a peak around 7 to 8 years of age, 5% to 7% of boys accordance with the findings at orchidopexy in childhood. In do not have both testes in a satisfactory scrotal position reviews of 10 575 orchidopexies, only 22% of the boys had when investigated at school examinations, but most of these bilateral undescended testes [97]. testes will descend during puberty (Fig. 1). Interestingly, The observation that testes thought to be completely Ward and Hunter [100] found a higher prevalence of descended at birth may “ascend” to a suprascrotal position undescended testes when examining the boys in school with time was noted by Villumsen and Zachau-Christiansen compared with the prevalence they found when examining [85] in 1966. In that series, 69 (1.6%) of 4300 boys had the same boys in the medical office. This illustrates some of unilateral (n = 51) or bilateral (n = 18) ascent of testes from a the diagnostic problems. Previously retractile testes were normal scrotal position at birth to a higher position by age 3 considered a normal variant, but this is probably not true for years (Fig. 1). Others have noted this same phenomenon in all retractile and late spontaneously descended testes. case reports with well-documented longitudinal data. Later Pathological studies provided evidence that some retractile in childhood, the ascended testis can be extremely difficult to discriminate from retractile testes, and in addition, the previous scrotal position may be hard to verify. Algarwal et al [98] retrospectively reviewed the charts of 122 boys (mean age, 5.4 years) who were referred for a suspected undescended testis and were found to have a retractile testis. A retractile testis was defined as a suprascrotal testis that could be manipulated easily into the scrotum and remained there without traction until the cremasteric reflex was induced. The boys were followed by annual examinations, to demonstrate the presence of retractile, descended (non retractile) or undescended testes, and the presence or absence of a taut or inelastic spermatic cord. Of 204 retractile testes, 61 (30%) descended (became nonretractile), 66 (32%) became undescended testes, and 77 (38%) remained retractile. Of the 62 retractile testes with a taut or inelastic spermatic cord, 35 (56%) became undescended testes. Boys in whom undescended testes developed were a mean of 4.9 years old. The authors concluded that a retractile testis is not Fig. 1 Prevalence of cryptorchidism (in percent; y-axis) in a normal variant given the associated 32% risk of becoming relation to age of the boys (in years; x-axis). Modified after Thorup an ascending or acquired undescended testis. and Cortes [99]. 2080 J. Thorup et al. testes may be abnormal. Han et al [102] found that although evidence that the rate of undescended testes has steadily been retractile testes have a significantly higher average number increasing with time during the last 50 years. of spermatogonia than cryptorchid testes, they have the same degree of tubule degeneration, suggesting that 2.4. Fertility aspects associated to cryptorchidism retractile testes undergo some abnormal histologic change. Another study shows that once a previously retractile testis Men with a history of cryptorchidism have an increased undergoes testicular ascent, it acquires the same decrease in risk of infertility. Outcomes related to infertility include the total and differential germ-cell count as primary undescend- paternity rate; semen analysis; measurement of serum LH, ed testes [103]. follicle-stimulating hormone, and inhibin B; and testicular Bremholm Rasmussen et al [104] followed a large cohort size. Testicular size and sperm density are positively of boys with bilateral cryptorchidism nonoperatively with correlated to germ-cell status in the cryptorchid testes in annual examinations through puberty. They reported the long- childhood [39,119]. Today, operation within the first year of term fertility potential of 45 men from this group whose testes life is often performed hoping to preserve testicular germ-cell were at the external ring, superficial inguinal pouch, and/or maturation [120]. Probably induced by the “minipuberty,” prescrotal positions but descended spontaneously between the neonatal gonocytes transform into type A spermatogonia ages 10 and 16 years (mean, 12 years). In these men, the testes during the first 12 months of age, a step that is now were reportedly dependent in the scrotum but were frequently postulated to be crucial for subsequent fertility, as these are borderline or subnormal in size (75%) and associated with the stem cells for spermatogenesis [119]. This step is blocked subnormal sperm concentration (53%). It is noteworthy that in undescended testis, and hence, to avoid this and when comparing the Danish data on newborns with hypothetically facilitate normal maturation, orchidopexy is cryptorchidism and high scrotal testes included from 2004 currently performed at 6 to 12 months of age in many centers by Boisen et al [80], along with the Danish data on school [97]. However, if there has been an underlying endocrino- children born in 1940 to 1966 by Blom [101],theybothfinda pathy causing inadequate maturation of the testis, merely 7% to 9% prevalence of abnormal testes. This may indicate putting the testis into the scrotum will not correct that that in some newborns, there may be scrotal testes that are endocrinopathy [119]. abnormal from the perspective of fertility potential. It is At birth, cryptorchid patients harbor germ cells in the important to remember that most infertile men have no history testes, but in reduced number compared with normal. From of corrected cryptorchidism, but some may have congenital about 15 months of age, germ cells may be lacking [39]. The endocrinopathy. Some high scrotal testes may be associated higher the age at orchidopexy, the higher the risk of finding with later infertility; however, there appears to have been no no germ cells on testicular biopsy tissue [121]. By 11 years change in prevalence during the last 50 years. of age, 35% of boys have no germ cells in their cryptorchid The aforementioned factors may explain why orchiopexy testes. The mean number of spermatogonia and gonocytes rates in different countries, such as Denmark, often exceed per tubule cross-section (mean-S/T) correlates positively the prevalence of congenital cryptorchidism. Ascended testes with sperm counts in adulthood [39,122,123]. When the S/T contribute 20% to 60% of orchidopexies [105-109]. Also, values bilaterally are normal at bilateral orchidopexy, a significant retractility is considered to be a risk factor for normal sperm output is expected in adulthood. If decreased testicular ascent [83]. At orchidopexy for the ascending S/T values are found, the risk of later infertility is high and testis, incomplete regression of the processus vaginalis is correlated with the S/T values. In cases where no germ cells often found, so that with somatic growth, the funiculus are apparent, the risk of later infertility is from 78% to 100%, remains short, retracting the testis up [110]. The orchidopexy depending on whether germ cells were absent in 1 or both rate has also not changed significantly in different publica- testes [123]. It appears that fertility is definitely related to the tions within the last 40 years. The cumulative orchidopexy characteristics of the undescended testis at orchidopexy. rate in different countries is stable around 2.4% to 3.8% Men who had bilateral cryptorchidism are more affected [89,111-115], with a minor transient increment of orchido- than unilateral cases. However, the position of the testes at pexy rates in Denmark and UK from 1980 to 1990 [89,116]. time of orchidopexy is also important. No fertility has been Also in New York area, the orchidopexy rate has been stable reported in men who underwent bilateral abdominal during the last decades [117]. In the State of Victoria, orchidopexy in childhood [124]. This is in agreement with Australia, there has been a true decline in the number of the fact that these testes have the most severely impaired orchidopexy operations done in children between 1999 and germ-cell number [125]. In an analysis of larger cohorts of 2006. This may represent a true decline in the incidence of adult men who underwent bilateral inguinal orchidopexy in disease, a failure of diagnosis, or a failure of management childhood, Lee and Coughlin [126] found that 35% (95% [118]. Therefore, with an overall worldwide prevalence of confidence level [CL], 29%-52%) did not achieve paternity undescended testes within the first years of life of 1% to 2%, in 1 year. This figure is in accordance with the findings of the orchidopexy rates around 2.4% to 3.8% fit well with the Cortes et al [123] that 54% (95% CL, 42%-66%) were figure that half the orchidopexies in childhood are performed infertile according to semen and hormonal analysis. In a on ascending or severely retractile testes. There is no review of 15 studies of men who had bilateral orchidopexy in Cryptorchidism and hypospadias 2081 childhood, only 21% of 323 men had at least 20 million mL among men born before 1959, and 78 million/mL for sperm cells/mL in the ejaculate, which, according to the men born after 1970). This finding was independent of the World Health Organization, is the lower limit of the age of the men and the years in which the semen sample reference range [39]. was delivered. However, a decline was not apparent in According to the histopathologic studies, it is assumed certain regions in the United States [135], in Australia that orchidopexy at an early age will improve the eventual [136], and in Finland [137]. Apparently, the Finnish men fertility. This is confirmed by data from 2 studies showing and American men had a high and unchanged semen quality that orchidopexy in bilateral cryptorchidism led to a normal over time [137]. sperm count in 76% of men if surgery was performed However, such assessment is confounded by ascertain- between 10 months and 3 years of age, compared with 26% ment bias in sampled population and methodological issues, following surgery between 4 and 14 years of age [127,128]. and most current evidence casts doubt on whether sperm Unilateral cryptorchidism carries an increased risk of outputs are indeed falling [35,138]. infertility in adulthood but is less than for bilateral cases. Lee et al [129] found that 10% (95% CL, 5%-15%) of men 3.2. Pathogenic aspects operated on in childhood for unilateral cryptorchidism did not achieve paternity in 1 year compared with 5% in a control Interestingly, in reports of such declines, no association group. This figure is in accordance with the findings of has been found between these declines and any type of Cortes et al [123] that 9% (95% CL, 3%-19%) were likely to endocrine disruptor [138,139]. Fetal environmental factors be subfertile according to semen and hormonal analysis. In a such as maternal heavy smoking may also influence the review of 14 studies of men who had unilateral orchidopexy fertility potential in cryptorchidism. Storgaard et al [140,141] in childhood, 70% of 747 men had at least 20 million sperm reported that sons of mothers who smoked more than 10 cells/mL in the ejaculate indicating a beneficial fertility effect cigarettes per day during pregnancy had reduced sperm of orchidopexy, given that only 49% with persistent density, total sperm output, inhibin B, and elevated follicle- unilateral cryptorchidism achieve that sperm density [39]. stimulating hormone levels [141]. These data have been Histopathologic studies show that in a proportion of cases confirmed and extended to show smaller testis size among with unilateral cryptorchidism, there is evidence of degen- men exposed to smoking in utero [142]. Thorup et al [89] erative changes in both testes [119]. In patients with no germ found that the absolute and age-related number of spermato- cells in the unilateral undescended testis at the time of gonia and gonocytes-per-tubule cross-section was signifi- surgery, 33% ended up with subfertile semen and hormonal cantly decreased in the undescended testes of boys whose parameters, even though the contralateral testis was mothers were heavy smokers compared with the same descended [123]. However, fertility in cryptorchidism may parameters in testes of boys whose mothers were nonsmo- also be related to the genes. Early growth response protein kers. Similarly, the group of cryptorchid boys where the may be such a gene responsible for fertility because it is mother was heavily smoking during pregnancy had signif- involved in regulating the secretion of LH, and in cases of no icantly increased risk of bilateral cryptorchidism (52%) expression of the gene, the number of type A dark compared with the group of boys where the mother did not spermatogonia was very low despite early surgery [130]. smoke (20%) [89]. Men who are heavy smokers show significantly lower sperm concentration and fertility index [143]. Other lifestyle factors, such as obesity, seem also to be of importance. Severely obese fertile men appear to have 3. Fertility in general reduced testicular function including significantly lower total sperm count compared with normal-weight men [144]. 3.1. Epidemiology However, whether this is cause or effect, that is, adiposity impairing spermatogenesis or reduced testicular function Based on a meta-analysis of publications mainly from promoting fat deposition, remains to be determined [144]. Europe and North America, Carlsen et al [131] indicated Well-known occupational risk factors such as direct that sperm concentration overall had declined by half exposure to pesticides among pregnant females employed during a 50-year period. In a reanalysis of this study, Swan in greenhouses may have little impact on prevalence rates on et al [132] found that the decline could have been even more cryptorchidism, because of the small numbers [145]. marked in European men. Subsequently, several study However, those risk factors may of course impair male groups retrospectively analyzed data from their individual offspring spermatogenesis of pregnant females and men with centers. Auger et al [133] detected a 2.1% decrease per year direct occupational exposure to pesticides. in sperm concentration during the period 1973 to 1992 In 1999, Moller and Skakkebaek [146] did a case control among potential semen donor candidates from Paris. Irvine study on 514 men with testicular cancer and 720 controls. et al [134] reported similar changes among Scottish men but They found that testicular cancer occurred more commonly also showed a birth-cohort effect, as a later year of birth was in men who had fathered no or only few children when the associated with a lower sperm concentration (eg, 98 million/ age of the man was taken into account. In conjunction with 2082 J. Thorup et al. studies of testicular histology and function, they found that dism, OR was 14.4 [147]. The similar trend was seen in a these data supported the hypothesis that male subfertility recent Swedish follow-up study on almost 17 000 operated was associated with a high risk of testicular cancer. The cryptorchid patients. For boys 0 to 6 years at surgery, OR most plausible explanation for this association was the was 2.02; for boys 7 to 9 years at surgery, OR was 2.35; for existence of causal factors that were common to both boys 13 to 15 years at surgery, OR was 5.06; and for boys 16 subfertility and testicular cancer. The epidemiology and to 19 years at surgery, OR was 6.24 [150]. In a meta-analysis biology of testicular cancer suggested that such common of the problem published by Walsh et al [151], they see the causes may have acted prenatally. same trend and conclude the following: in males with cryptorchidism, prepubertal orchidopexy may decrease the risk of testicular cancer. Although preservation of fertility 4. Testicular cancer and self-examination are important, this indication is equally important for early surgical intervention. There are actually 4.1. Cancer risk in cryptorchid testes few studies in this meta-analysis, including the study by Moller [147] previously presented, but not the Swedish Testicular cancer is the most common cancer in men aged study. The OR of testicular cancer in the contralateral 20 to 34 years, and cryptorchidism is the key accepted risk descended testis in unilateral undescended testis in the study factor carrying a relative risk between 3.7 and 7.5 times by Moller [147] was 1.9. In the study by Swerdlow et al higher than the background population. Statistically, 5% of [152], it was 2.1, but in the other studies, the figures were testicular cancers are associated with cryptorchidism too low or the follow-up too short to conclude. [124,147]. Testicular maldevelopment or de-differentiation is identified in a large fraction of men with testicular cancer 4.2. Epidemiology of testicular cancer in general and intratubular germ-cell neoplasia [148,149]. Intratubular germ-cell neoplasia (also known as carcinoma in situ), is a There has been an increase in the incidence of testicular histologic premalignant pattern that can be seen in cancer in many Western countries during the past 40 years cryptorchid testis in early childhood. In a review of 6 studies (Table 4) [153,154], and the global incidence of testicular on 2800 prepubertal testicular biopsies from cryptorchid cancer has doubled during the past 3 decades [153-155]. The testes, intratubular germ-cell neoplasia was seen in 0.36% age-standardized incidence rate is a summary measure of a [39]. In a study by Cortes et al [123], intratubular germ-cell rate that a population would have if it had a standard age neoplasia was found in 4% of 182 patients with intra- structure. Age-standardized incidence rates are used to abdominal testes, abnormal external genitalia, and/or compare incidence rates of disease between populations abnormal karyotype (45,X/46,X del Y (q21) and 46,XY/ with different age distributions, as is the case with testicular 47,XYY) but in none of 1281 in the rest of the cryptorchid cohort. This means that patients with intra-abdominal testes, abnormal external genitalia, and/or abnormal karyotype may be of special risk in development of cancer, and biopsy is Table 4 The age-standardized incidence rates (per 100 000) recommended at orchidopexy. of testicular cancer for 30 years from selected countries [148] The risk of developing testicular cancer in cryptorchid Country/area in country Incidence men has not eliminated by orchidopexy, but it appears to 1975 1985 1995 2007 decrease the risk [147,150,151]. In the epidemiologic studies of testicular germ-cell cancer in 514 cases and 720 controls Canada, Alberta 3.7 3.6 4.2 5.2 Egypt, Gharbiah NA NA NA 0.5 by Moller [147], an increased cancer risk associated with USA, SEER: non-Hispanic white 3.8 5.0 5.5 6.3 cryptorchidism was found to be higher in bilateral than in USA, SEER: black 0.8 0.8 1.0 1.3 unilateral cryptorchidism (OR, 4.9 and 2.9, respectively). China, Hong Kong 1.3 1.0 1.7 1.6 Of the 21 cases with unilateral cryptorchidism, the cancer Israel, Jews 1.9 2.3 3.3 4.1 occurred in the undescended (ipsilateral) testis in 14 cases Singapore, Chinese 0.8 0.9 0.9 0.9 and in the normally descended (contralateral) testis in 7 Denmark 7.0 8.4 9.8 9.2 cases. The relative cancer risk was therefore 3.9 in the Finland 1.6 2.0 2.7 3.7 ipsilateral and 1.9 in the contralateral testis. This also Ireland NA NA NA 5.6 supports the finding that in some cases, unilateral cryptor- Norway 4.5 6.5 8.6 9.6 chidism may be a bilateral disease, thus carrying a risk of Sweden 3.1 3.9 4.9 5.3 bilateral neoplasia. Another interesting finding of this large Switzerland, Geneva 5.0 6.1 6.7 6.9 Netherlands, Eindhoven NA 3.0 4.4 5.6 case/control study was that the younger the boy was at UK, Scotland 3.9 5.0 6.3 7.6 operation, the lower the OR for later testicular cancer. For Australia, New South Wales 3.0 3.7 5.1 5.8 boys 0 to 9 years at surgery, OR was 1.1; for boys 10 to 14 New Zealand NA 5.4 5.8 6.8 years at surgery, OR was 2.9; for boys older than 15 years at NA indicates not available. surgery, OR was 3.5; and adults with persisting cryptorchi- Cryptorchidism and hypospadias 2083 cancer. The age-standardized incidence rate is expressed as 5. Conclusion the number of new cases per 100 000 person years and is calculated first by estimating the age-specific rates and then It has been hypothesized that poor semen quality, testis applying these rates to the reference population. The most cancer, undescended testis, and hypospadias are symptoms frequently used reference population is the world standard of one underlying entity—the so-called TDS—leading to population [148]. There is marked geographical variation in increasing male fertility impairment. Though there has been the age-standardized incidence rate for testicular cancer, an increase in the incidence of testicular cancer in many ranging from as low as 0.5/100 000 in Egypt to as high as Western countries during the past 40 years, hypospadias 9.2/100 000 in Denmark (Table 4) [153,154]. For most rates may or may not have changed with certainty during populations, the incidence of seminoma was slightly greater the same period. Recent studies also demonstrate that sperm than that of nonseminoma [156]. There was no clear output is probably not declining across the globe, at the evidence of an increase in incidence among Singapore same time there is increasing recognition of male infertility Chinese, where the age-standardized incidence rate is and of impairment of male fertility related to obesity and virtually unchanged during the past 30 years (Table 4). smoking. There is no evidence that the rates of undescended The incidence of testicular cancer has continued to increase testes have steadily been increasing with time during the in almost all populations worldwide during the past 40 years, last 50 years. In more than 95% of cases, hypospadias is not increases being strongest and most consistent among high- associated with cryptorchidism, and major differences in incidence populations [156]. relation to pathogenesis of the 2 entities dominate. Genes Schwartz [157] hypothesized recently that the major and hormones influence structural development both features of the descriptive epidemiology of testicular cancer directly and indirectly. Placental abnormality may occa- were all associated with exposure to ochratoxin A. Ochratoxin sionally be related to the pathogenesis of cryptorchidism A is a naturally occurring contaminant of cereals, pig meat, and and hypospadias, as it is also the case in many other other foods and is known to induce adducts in testicular DNA congenital malformations. The hypothesis that the abnormal as a genotoxic carcinogen in animals. Incidence rates for location of the testis exposes the testis to infertility and testicular cancer in 20 countries were significantly correlated malignant transformation is supported by the findings of with the per-capita consumption of coffee and pig meat [157]. early treatment lowering the risk of both infertility and testicular cancer. 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