Comparison of the effects of contraceptive steroid formulations containing two doses of estrogen on pituitary function.

A pituitary stimulation test with gonadotropin-releasing hormone (GnRH) and thyrotropin-releasing hormone (TRH) was undertaken to determine (1) whether pituitary responses to GnRH vary in individual women taking oral contraceptive steroids over time, (2) whether a less suppressive pituitary gonadotropin effect is produced by formulations containing less than 50 microgram of estrogen, and (3) to obtain more information concerning prolactin secretion in users of oral contraceptive steroids. The same subjects who had had a suppressed luteinizing hormone (LH) and follicle-stimulating hormone (FSH) response 6 to 9 months previously also had a suppressed response, indicating that this effect persists over time. Contraceptive formulations containing less than 50 microgram of estrogen have a lesser suppressive effect on LH release than do formulations containing 50 microgram of estrogen or more. The basal prolactin (PRL) response as well as the maximal PRL response to TRH were found to be significantly greater in subjects using oral contraceptives than in the control subjects. However, no difference in PRL response was found between the subjects using low or high doses of estrogen fomulations.