Oral contraceptives and prolactinomas: a case-control study.

The increase in the number of newly diagnosed cases of prolactinomas seems to coincide with the use of oral contraceptives during the past two decades. The following retrospective case-control study was undertaken in an attempt to disprove a null hypothesis of relationship between oral contraceptive use and prolactinomas. Each of 70 patients operated upon for removal of a prolactinoma was closely matched for age, gravidity, and year of final diagnosis with one patient in each of three control groups. The control groups selected were constituted, respectively, of patients with secondary amenorrhea and normal prolactin levels, patients with normal ovulatory cycles consulting for infertility, and subjects without medical or gynecologic problems. No statistically significative differences were found in the exposure rates to oral contraceptives among four groups. This study thus failed to reveal a significant association between prolactinomas and oral contraceptives but, given the sample size, a relative risk lower than 3.32 cannot be demonstrated or disproved.