Male and female external genitalia appear identical early in gestation. Testosterone exposure at 8–12 weeks’ gestation causes male differentiation. Female fetuses virilize if their adrenals secrete excessive levels of androgens, as occurs in congenital adrenal hyperplasia due to 21-hydroxylase deficiency. This can be ameliorated by administering dexamethasone to the mother. A study by Goto et al. in this issue of the JCI provides a rationale for this treatment by demonstrating that the fetal hypothalamic-pituitary-adrenal axis is fully functional when the genitalia differentiate (see the related article beginning on page 953). Dexamethasone suppresses this axis, reducing abnormal secretion of adrenal androgens. Their results also show that cortisol synthesis by the fetal adrenal decreases after this period, allowing the adrenal to secrete high levels of dehydroepiandrosterone, an androgen precursor. However, this does not virilize female fetuses because androgens are aromatized to estrogens in the placenta. Thus normal sexual differentiation requires exquisite timing of fetal cortisol and androgen secretion versus placental capacity for aromatization.
Perrin C. White
Usage data is cumulative from May 2023 through May 2024.
Usage | JCI | PMC |
---|---|---|
Text version | 149 | 24 |
83 | 21 | |
Figure | 58 | 3 |
Citation downloads | 9 | 0 |
Totals | 299 | 48 |
Total Views | 347 |
Usage information is collected from two different sources: this site (JCI) and Pubmed Central (PMC). JCI information (compiled daily) shows human readership based on methods we employ to screen out robotic usage. PMC information (aggregated monthly) is also similarly screened of robotic usage.
Various methods are used to distinguish robotic usage. For example, Google automatically scans articles to add to its search index and identifies itself as robotic; other services might not clearly identify themselves as robotic, or they are new or unknown as robotic. Because this activity can be misinterpreted as human readership, data may be re-processed periodically to reflect an improved understanding of robotic activity. Because of these factors, readers should consider usage information illustrative but subject to change.