EFFECTS OF PROGESTERONE ON THE SERUM LEVELS OF FSH AND LH IN POSTMENOPAUSAL WOMEN TREATED WITH OESTROGEN

Abstract

ABSTRACT The effect on the serum levels of FSH and LH after the intramuscular administration of 10 or 100 mg progesterone in oil was studied in twenty postmenopausal women. Immunoreactive FSH and LH in the serum were assayed by a radioimmunosorbent technique. The administration of progesterone alone to ten women did not result in any major changes in the serum levels of the gonadotrophins. Ethinyloestradiol in an oral dose of 100 μg daily to the other ten women significantly decreased the high postmenopausal levels of gonadotrophins. After four weeks of treatment levels usually seen in women of fertile age were found. The relative decrease for FSH was greater than for LH. When 10 mg progesterone was administered after four weeks of oestrogen treatment, an increase in the serum levels of LH was found in all the six women studied associated with a sharp conspicuous LH peak in four of them. There was also a small increase in the serum levels of FSH. After the larger dose of progesterone, i. e. 100 mg, only one of five women showed an LH peak combined with a minor FSH increase. In the other four subjects, there was only a minor increase in the serum levels of LH which was not of the same magnitude as that found with the 10 mg dose. The FSH levels were, if anything, decreased. It thus appears that progesterone in low doses was more effective in inducing a release of gonadotrophins in postmenopausal women treated with oestrogen. This suggests that in this experimental situation progesterone does not act as an »antioestrogen[« and that this hormone, particularly in low doses, has a stimulating or facilitating effect on the hypothalamic-pituitary system.