EFFECTS OF OESTROGEN ON SERUM LEVELS OF LH AND FSH

Abstract

ABSTRACT The acute effects on the serum levels of LH and FSH after the administration of some oestrogen preparations were investigated in oligoamenorrhoeic women, in postmenopausal women and in men. Immunoreactive LH and immunoreactive FSH in the serum were assayed by a radioimmunosorbent technique. The diurnal rhythm in the secretion of the gonadotrophins was first studied. No significant circadian variation in either LH or FSH levels in the serum of hospitalized women or healthy men was found with this radioimmunoassay procedure. The intravenous or intramuscular administration of 17β-oestradiol in doses from 5 μg to 5 mg resulted in a decrease in the serum levels of LH in 14 of 15 women studied and in the serum levels of FSH in 10 of 12 women. This can be explained by a negative feedback effect on the hypothalamic-pituitary system during the period of observation. The decrease in the serum gonadotrophin levels was as a rule more pronounced for LH than for FSH. No positive feedback effect on the hypothalamic-pituitary system following oestrogen treatment was observed. In men insignificant and variable changes in the serum gonadotrophin levels were found. This could possibly be explained by the low oestrogen doses used.