Age-specific changes in sex steroid biosynthesis and sex development.
Normal male sex development requires the SRY gene on the Y chromosome, the regression of Müllerian structures via anti-Müllerian hormone (AMH) signalling, the development of the Wolffian duct system into normal male internal genital structures consequent to testosterone secretion by the testicular Leydig cells, and finally, sufficient activation of testosterone to dihydrotestosterone by 5alpha-reductase. All these events take place during weeks 8-12 of gestation, a narrow window of sexual differentiation. Recent studies in human fetal development have demonstrated the early fetal expression of the adrenocorticotrophic hormone (ACTH) receptor and all steroidogenic components necessary for the biosynthesis of cortisol. These findings provide compelling evidence for the assumed pathogenesis of congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency, diminished feedback to the pituitary due to glucocorticoid deficiency, subsequent ACTH excess, and up-regulation of adrenal androgen production with subsequent virilization. Another CAH variant, P450 oxidoreductase deficiency, manifests with 46,XX disorder of sex development (DSD), i.e., virilized female genitalia, despite concurrently low circulating androgens. This CAH variant illustrates the existence of an alternative pathway toward the biosynthesis of active androgens in humans which is active in human fetal life only. Thus CAH teaches important lessons from nature, providing privileged insights into the window of human sexual differentiation, and particularly highlighting the importance of steroidogenesis in the process of human sexual differentiation.
Krone
Nils
N
Division of Medical Sciences, Institute of Biomedical Research, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Hanley
Neil A
NA
Arlt
Wiebke
W
D000312:Adrenal Hyperplasia, Congenital / Q000145:classification / Q000196:embryology / Q000378:metabolism; D000375:Aging / Q000378:metabolism; D000818:Animals; D025461:Feedback, Physiological; D005260:Female; D023961:Gonadal Dysgenesis, 46,XX / Q000145:classification / Q000196:embryology* / Q000378:metabolism; D012739:Gonadal Steroid Hormones / Q000096:biosynthesis* / Q000502:physiology*; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000196:embryology / Q000502:physiology; D008297:Male; D009251:NADPH-Ferrihemoprotein Reductase / Q000172:deficiency; D010913:Pituitary-Adrenal System / Q000196:embryology / Q000502:physiology; D046468:Sexual Development / Q000235:genetics / Q000502:physiology; D013255:Steroid 21-Hydroxylase / Q000096:biosynthesis
D012739:Gonadal Steroid Hormones; D013255:Steroid 21-Hydroxylase; D009251:NADPH-Ferrihemoprotein Reductase