Steroid secretion by human early embryos in culture.

The ability of in-vitro fertilized human embryos to secrete oestradiol in culture in the presence of precursor androgen was demonstrated in four independent cultures. Varying amounts of oestradiol were detected and secretion was observed as early as days 5-8 post-fertilization. The pattern of human chorionic gonadotrophin secretion was similar to oestradiol secretion for individual embryos. In one additional culture, secretion of oestradiol and progesterone was observed.