A longitudinal analysis of premenopausal bone loss in healthy women and women with hyperprolactinemia.

In this report we describe longitudinal measurements of forearm and spinal bone mineral in healthy women and women with hyperprolactinemia. One hundred and ten women underwent yearly assessment of forearm and spinal bone mineral by single photon absorptiometry and computed tomography for an average of 4.7 yr. At entry into the study, women with hyperprolactinemic amenorrhea had 21% lower spinal bone mineral and 2.5% lower forearm bone mineral than healthy premenopausal women. Despite decreased estradiol levels (31 +/- 23 pmol/L), spinal bone in women with hyperprolactinemic amenorrhea did not change over time (+0.08%/yr; P = 0.89). In contrast, spinal bone in healthy women with regular menses (mean age, 34.6 +/- 6.6 yr) decreased significantly (1.7%/yr; P = 0.01). Cortical bone in the forearm did not change in either group. The hyperprolactinemic subjects had higher body mass index (28 +/- 6 vs. 24 +/- 4 kg/m2) and serum testosterone (0.5 +/- 0.2 vs. 0.39 +/- 0.16 pmol/L) than control subjects, but neither parameter correlated with bone loss. Although 64% of the hyperprolactinemic subjects had serum estradiol levels below 30 pmol/L, there was no correlation between estradiol or duration of amenorrhea and bone loss. Women with normal PRL levels and regular menses 3-9 yr after treatment of hyperprolactinemia had significantly lower spinal bone mineral (147 +/- 28 mg/mL) than healthy premenopausal women (169 +/- 29 mg/mL) and showed no change in spinal bone (+0.3%/yr; P = 0.67) over 5 yr. Despite significant hypoestrogenemia, women with hyperprolactinemic amenorrhea did not evidence a rapid decline in spinal bone. Restoration of gonadal function was not associated with normalization of bone mineral. The bone loss that accompanies hyperprolactinemia is not comparable to that which occurs after oophorectomy or menopause. These findings raise important questions about the importance of osteopenia as an indication for treatment of hyperprolactinemic amenorrhea.