Neonatal androgen abolishes clock-timed gonadotrophin release in prepubertal and adult female hamsters.

Testosterone propionate (100 micrograms) or oil was injected within 24 h of birth. At 25 days of age blood samples were obtained at 14:00, 17:00 and 20:00 h. There was a significant increase in serum LH, FSH and progesterone concentrations between 14:00 and 17:00 h in the controls, followed by a decrease at 20:00 h. These rhythms were absent in testosterone propionate-injected animals. Ovariectomy of adults was followed by similar increases of LH and FSH in androgenized and oil-injected females (gonadectomy response) but the large surge of gonadotrophins observed in controls 1 day after implantation of an oestradiol-containing capsule (positive feedback) was not detectable in androgenized females. These results show that the initial effects of neonatal androgenization on cyclic gonadotrophin release in the female are present before puberty and are separable from effects on steroid modulation of gonadotrophin secretion.