Sex-Dependent Changes in Pituitary 5α:-Dihydrotestosterone and 3α-Androstanediol Formation During Postnatal Development and Puberty in the Rat

The in vitro conversion of testosterone-l,2-H³ to 5α-dihydrotestosterone (DHT) and 3α-androstanediol (DIOL) was studied in pituitary and brain during development in normal male and female rats, and after gonadectomy and hormone replacement at different ages. At birth, pituitary DHT and DIOL formation was equal in both sexes, but significant sex-specific changes occurred during development. In females the formation of both metabolites rose dramatically with age to reach a peak value between 10 and 15 days; the latter values exceeded that obtained in adult prostate. Subsequently there was a steep fall to about 10 times lower levels at 40 days. In male rats, pituitary DHT formation increased only slightly up to 10 days of life, then decreased until day 25 but showed a significant second rise between 30 and 34 days. At all of these ages, activity was higher than in adult life. Fluctuations as seen in the pituitary were not seen in hypothalamus, midbrain, or cerebral cortex. Gonadectomy at 5, 18, 24, or 29 days of age resulted in dramatic increases in pituitary DHT and DIOL formation as measured 10 days later. The postgonadectomy levels were equal in both sexes gonadectomized at 5 days and measured at day 15, but were higher in females than in males gonadectomized at the three other ages. With increasing age, there was a decline in postgonadectomy rises; this occurred earlier in males than in females. Treatment with testosterone propionate (TP; 40 μg/100 g body wt/day) prevented the postgonadectomy rises in both males and females, but estradiol benzoate (EB) in doses that stimulate uterine weight (0.05 α.g/100 g body wt/day) had only a very weak inhibitory effect. Around 28 to 37 days of age, TP was less effective than at other ages in suppressing the postgonadectomy rise. The sex-specific changes and responses to gonadectomy and sex hormones in pituitary DHT and DIOL formation during development closely parallel the sex-specific modifications in pituitary gonadotropin secretion known to occur during development in normal rats and as a consequence of the latter hormonal changes. The correlation of these changes with FSH levels under similar conditions is particularly striking. (Endocrinology94: 1265, 1974)