Serum prolactin, gonadotrophin and oestrogen levels in women receiving hormone replacement therapy.

Prolactin, oestrone, oestradiol, FSH and LH concentrations have been determined in postmenopausal women receiving different forms of hormone replacement therapy. While the serum oestrogen levels achieved were sufficient to cause a significant decrease in circulating FSH and LH levels, no significant change in prolactin concentrations was found. Two other findings are of interest: despite the absolute concentrations achieved, the ratio of FSH to LH and the ratio of oestradiol to oestrone did not change significantly on any of the hormone formulations used; and while FSH and LH were both suppressed to a significant degree on therapy neither was suppressed to premenopausal values suggesting the possibility of a 'female inhibin' in the normal regulation of gonadotrophin secretion.