Objective: To study the clinical cause and course of hyperprolactinemia in postmenopausal women. Design: Retrospective case-note study. Setting: Tertiary care hospital. Patient(s): Six postmenopausal women with hyperprolactinemia. Main Outcome Measure(s): Clinical history and physical examination, serum levels of PRL, LH, FSH, computed tomography (CT) of the pituitary gland before and after treatment with bromocriptine. Result(s): At presentation, the mean age was 57.5 +/- 7.5 SD years. The mean level of PRL was 1,427 +/- 1,599 ng/mL (1,427 +/- 1,599 mu g/L). All women suffered from secondary amenorrhea for a mean duration of 31.8 +/- 5.6 years. Five of six had galactorrhea at some time in the past. Pituitary imaging revealed a pituitary macroadenoma in four women, an enlarged sella suggestive of a pituitary macroadenoma in one woman, and a microadenoma in one. After treatment with bromocriptine, the PRL level decreased in all women to within normal limits. Five of six women developed hot flushes after the PRL level returned to normal. Conclusion(s): Most cases of hyperprolactinemia in postmenopausal women are due to macroadenoma rather than microadenoma, the common finding in younger women. The clinical course is suggestive of a prolonged disease that was not detected earlier, although clinical signs were present. These findings are suggestive of an enlargement of microadenomas to macroadenomas as time passes. (C) 1997 by American Society for Reproductive Medicine.