The effect of contraceptive steroids on hypothalamic-pituitary function.

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.