Journal of Pediatric Surgery (2010) 45, 2074–2086 www.elsevier.com/locate/jpedsurg Review articles What is new in cryptorchidism and hypospadias—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 Urology, 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 semen quality, 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 testicular cancer 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 male infertility 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