Abstract
Cryptorchidism, or undescended testis, is a well-known risk factor for testicular cancer and impaired semen quality in adulthood, conditions which have their origins in early fetal and postnatal life. In human pregnancy, the interplay of testicular and placental hormones as well as local regulatory factors and control by the hypothalamic-pituitary (HP) axis, lead to testicular descent by term. The normal masculine development may be disrupted by environmental factors or genetic defects and result in undescended testes. Minipuberty refers to the postnatal re-activation of the HP-testicular (T) axis after birth. During the first weeks of life, gonadotropin levels increase, followed by activation and proliferation of testicular Leydig, Sertoli and germ cells. Consequent rise in testosterone levels results in penile growth during the first months of life. Testicular size increases and testicular descent continues until three to five months of age. Insufficient HPT axis activation (e.g., hypogonadotropic hypogonadism) is often associated with undescended testis and therefore minipuberty is considered an important phase in the normal male reproductive development. Minipuberty provides a unique window of opportunity for the early evaluation of HPT axis function during early infancy. For cryptorchid boys, hormonal evaluation during minipuberty may give a hint of the underlying etiology and aid in the evaluation of the later risk of HPT axis dysfunction and impaired fertility. The aim of this review is to summarize the current knowledge of the role of minipuberty in testicular development and descent.
Highlights
Testicular descent initiates during early fetal development and finalizes during the first postnatal months
Most cohort studies have used criteria developed by John Radcliffe Hospital Study group, in which the testicular position is classified in reference to anatomical landmarks as “non-palpable,” “inguinal,” “suprascrotal,” and “high scrotal,” whereas testes that lie in the bottom of the scrotum are considered normal (Figure 1) [5]
We evaluate and summarize the current knowledge of the role of the HPT axis in pre- and postnatal testicular descent in humans and compare the differences in minipuberty between healthy and cryptorchid boys
Summary
Testicular descent initiates during early fetal development and finalizes during the first postnatal months. This complex process is regulated by multiple genetic, anatomical and hormonal factors and environmental factors may influence its course. In his landmark paper, Scorer considered testes that were within the 4 cm distance from the pubic bone as undescended among term boys [3], which roughly corresponds with the 2.5th centile at birth [4]. Most cohort studies have used criteria developed by John Radcliffe Hospital Study group, in which the testicular position is classified in reference to anatomical landmarks as “non-palpable,” “inguinal,” “suprascrotal,” and “high scrotal,” whereas testes that lie in the bottom of the scrotum (scrotal) are considered normal (Figure 1) [5]. There seems to be some evidence of reduced testicular growth among boys with retractile testes [9]
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