Infertility in Cryptorchidism Is Linked to the Stage of Germ Cell Development at Orchidopexy

Pediatric urologic conditions, including urinary infections

Genitourinary complaints are common in children, and the busy primary care provider must determine initial treatment and assess need for specialty referral. Many complaints are self-limited, but some represent disorders that can threaten organ function. In this article, an initial approach in the primary care office and a guide to specialty referral for pediatric urologic conditions of the urinary tract, male genitalia, and female genitalia are suggested.

[Cryptorchidism: from physiopathology to infertility]

Cryptorchidism is a defect of testicular descent. Hormonal, genetic and environmental factors might also contribute to the aetiology of cryptorchidism and its increased incidence in recent years in industrialised countries. Cryptorchidism itself might be considered a complex disease. This testicular pathology represents the best-characterized risk factor for reduced fertility and testicular cancer. The purpose of this review is to better understand physiopathology and mechanisms of infertility in men with history of cryptorchidism.

Cryptorchidism

Cryptorchidism is a very common anomaly of the male genitalia, affecting 2%-4% of male infants and is more common in premature infants. There are two separate stages of testicular descent. The first stage occurs at 8-15 weeks' gestation in the human fetus and is characterized by enlargement of the genito-inguinal ligament, or gubernaculum, and regression of the cranial suspensory ligament. The testis remains close to the future inguinal region as the fetal abdomen grows. Leydig cells in the testis produce insulin-like hormone 3, which stimulates the caudal gubernaculum to grow and become thicker. Mullerian inhibiting substance may have a role in the first phase of descent by stimulating the swelling reaction in the gubernaculum. The second phase of testicular descent requires migration of the gubernaculum and testis from the inguinal region to the scrotum, between 25 and 35 weeks' gestation. The genitofemoral nerve releases calcitonin gene-related peptide, a neurotransmitter that provides a chemotactic gradient to guide migration. The exact cause of cyrptorchidism remains elusive. Information is mainly derived from animal studies (especially in rodents), which may not extrapolate to the human setting. These findings, however, do have some similarities among mammalian species. The current recommended timing for orchidopexy is between 6 and 12 months of life in an effort to preserve the spermatogonia--the stem cells for subsequent spermatogenesis. Despite surgical treatment by orchidopexy, the long-term outcome still remains problematic and controversial. Impaired fertility (33% in unilateral cases and 66% in bilateral undescended testes) and a cancer risk 5-10 times greater than normal is observed over time. Further research into the cause and management of undescended testes is necessary.

Cryptorchidism: pathogenesis, diagnosis, treatment and prognosis

Cryptorchidism is a common genital anomaly diagnosed at birth or during childhood. Genetic and/or environmental factors that alter expression or function of hormones crucial for testicular descent, insulin-like 3, and testosterone, may contribute to cryptorchidism. When identified at birth, surgical treatment is indicated by 6 months of age if testes fail to descend, or at the time of diagnosis in older children. A laparoscopic approach is preferred for abdominal testes. Early surgical therapy may reduce the risk of subfertility and/or malignancy.

A critical appraisal of the evidence for improved fertility indices in undescended testes after gonadotrophin-releasing hormone therapy and orchidopexy

Male fertility depends on the transformation of gonocytes into dark adult spermatogonia, during the first 3 months of postnatal life, and this is an androgen-dependent process. This essential developmental step appears to be defective in undescended testes, and in many patients orchidopexy alone (at the age it is currently performed) does not improve fertility indices, either because it does not address the underlying pathophysiology or the surgery is performed too late. Hormone therapy with gonadotrophin-releasing hormone creates a rise in testosterone levels, copying the postnatal gonadotrophin surge. This can improve germ cell numbers, with the implication of enhanced longer-term fertility. The role of hormone therapy has been controversial, and although favoured at the European Society of Paediatric Urologists' workshops in 2008 and 2009, it is not routine clinical practice in the UK or other countries. We performed a critical appraisal of the key papers in the world literature to evaluate the level of evidence for improved fertility indices, semen analysis and paternity rates following hormone therapy in undescended testes. We suggest that the evidence is sufficiently strong to recommend a change in clinical practice.

Factors controlling testis descent

Descent of the testis from an intra-abdominal site in foetal life to an extracorporeal location after birth is a mandatory developmental process to ensure that the mature testis promotes normal spermatogenesis. The two phases of transabdominal and inguinoscrotal descent occur approximately during the first and last thirds of gestation respectively. Key anatomical events to release the testis from its urogenital ridge location and to guide the free gonad into the scrotum are the degeneration of the cranio-suspensory ligament and a thickening of the gubernaculum. Androgens play a role in both these processes, particularly with respect to enabling the testis to traverse the inguinal canal in the final phase of descent. Experiments in animals suggest that androgens mediate this effect via the release of calcitonin gene-related peptide by the genitofemoral nerve, but direct evidence for such a mechanism is lacking in humans. The transabdominal phase of descent is under the control of insulin-like 3 (INSL3), a product of the Leydig cells. Definitive evidence of its role in rodent testis descent is illustrated by the phenotype of bilateral cryptorchidism in Insl3-/- null mice. Circulating levels of INSL3 are higher in boys at puberty, are undetectable in girls and are lower in boys with undescended testes. A minority also have a mutation either in the INSL3 gene or affecting its receptor gene, relaxin/insulin-like family peptide receptor 2 (LGRF8). Other factors that may play a role in testis descent include the anti-Mullerian hormone and members of the HOX gene family. Evidence that the prevalence of undescended testis may be increasing provides a phenotypic readout for the effects of postulated chemicals in the environment interfering in some way with the action of factors that control testis descent. Epidemiological studies point to profound geographical variations in prevalence in countries such as Denmark and Finland. Associations have been found with levels of chemicals labelled as endocrine disruptors being higher in breast milk samples from mothers with cryptorchid boys when compared with controls. The adverse effects of these compounds (e.g. bisphenol A) can be replicated in the offspring of dams exposed during pregnancy. A sensitive marker of an anti-androgen effect of a compound is a reduction in the anogenital distance, an anthropometric measurement that is significantly greater in males compared with females. The observation of an association between the anogenital distance in infant boys and the level of pesticides in the urine of their mothers in late gestation indicates that this has the potential to be a useful surrogate marker of the effects of environmental chemicals on testis descent in human population studies. The rightful place for the testis at birth is in the scrotum in order to provide the temperature differential essential for normal spermatogenesis. Appropriate screening programmes and early surgical intervention are the prerequisites to ensure optimal fertility in adulthood and a considerably lessened risk of testis cancer.

Differences in testicular development between 5alpha-reductase 2 deficiency and isolated bilateral cryptorchidism

PURPOSE

We demonstrated that infertility develops in most patients with steroid 5alpha-reductase 2 deficiency.

MATERIALS AND METHODS

We compared the testicular histopathology of boys with steroid 5alpha-reductase 2 deficiency to that of boys with isolated bilateral cryptorchidism.

RESULTS

Testes with steroid 5alpha-reductase 2 deficiency lacked spermatocytes but had Ad spermatogonia and a normal germ cell count. In contrast, bilateral cryptorchid testes had severe germ cell depletion and the majority lacked Ad spermatogonia.

CONCLUSIONS

In patients with steroid 5alpha-reductase 2 deficiency the impaired second step of germ cell maturation results in defective transformation of spermatogonia into spermatocytes. The position of the undescended testis appears to have no major pathological impact on the development of germ cells in patients with steroid 5alpha-reductase 2 deficiency.