The ontogenesis of reproductive hormones in the female embryo of the domestic fowl

The ontogenesis of sexual hormones and the responsiveness of both ovaries to LH were studied during the last third of incubation of chick embryos. Pituitary LH and FSH and serum 17 beta-estradiol increase through development to reach a plateau near hatching. Serum LH and the ovarian progesterone content show maxima on Day 19 of incubation. Serum progesterone levels are highly variable, with apparently unchanged values during development. Ovine LH was able to stimulate progesterone secretion in vitro in the left ovary at all times during development. LH stimulation of 17 beta-estradiol secretion in vitro is high on Day 13 in both ovaries but lower at later stages.