The effect of contraceptive steroids on hypothalamic-pituitary function

Abstract

A study was performed to obtain additional information about the effects of oral contraceptives on pituitary function. A sequential pituitary stimulation test (SST) was used to study normal control women who then received either a combination pill with 50 mug of ethinyl estradiol or an injectable or oral progestin for three weeks, after which the test was repeated. The same test was also performed on five long-term oral contraceptive users. The SST consists of measurement of growth hormone (GH), thyroid-stimulating hormone (TSH), prolactin (PRL), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) at frequent intervals after stimulation by hypoglycemia, thyrotropin-releasing hormone, and gonadotropin-releasing hormone. GH and TSH release following stimulation were unaffected by the use of contraceptive steroids, while PRL release was increased by both the combination pill and the progestin alone. LH and FSH release was decreased in the three short-term and most of the long-term users of the combination pills but was not decreased in two of the long-term users as well as in those receiving the progestin alone. These results indicate that the combination oral contraceptives have a direct effect upon the pituitary gland, causing an increase in prolactin release and a decrease in gonadotropin release. This effect varies among individuals receiving the same formulation and may be related to the development of syndrome of postpill amenorrhea-galactorrhea.

PIP: The effect of oral contraceptives (OCs) on hypothalamic-pituitary function was examined by use of a sequential pituitary stimulation test (SST) on normal control women who then received either a combination pill with 50 mcg ethinyl estradiol or an injectable or oral progestin for 3 weeks. The same test was performed in 5 long-term OC users. In the SST the patients are stimulated by hypoglycemia, thyrotropin-releasing hormone, and gonadotropin-releasing hormone after which growth hormone (GH), thyroid stimulating hormone (TSH), prolactin (PRL), luteinizing hormone (LH), and follicle stimulating hormone (FSH) are measured at frequent intervals. GH and TSH release following stimulation were unaffected by use of OCs, while PRL release was increased by both types of OCs. LH and FSH release was decreased in 3 short-term and in most of the long-term users of combined OCs but was unaffected in 2 long-term users and in all of the progestin-only users. These results suggest a direct effect on the pituitary by combined OCs causing increased prolactin release and a decrease in gonadotropin release. This effect varies among individuals and possibly is related to the development of postpill amenorrhea-galactorrhea. Further study on lower dose pills is suggested. Discussion of these results focused on the small numbers used in the study and possible alternative explanations for results.