Osteocalcin levels in patients with microprolactinoma before and during medical treatment

Osteocalcin (OC) concentration, a specific index of bone formation, was measured in 29 female patients with microprolactinoma (serum prolactin, PRL: 105 ± 10.9 ng/ml; mean ± SE). Mean OC levels were significantly lower than in controls (1.7 ± 0.2 vs 5.1 ± 0.3 ng/ml; p <0.001), being below the normal range in 28 out of 29 patients. All patients were treated with dopaminergic agents (dihydroergocriptine, bromocriptine or cabergoline). After treatment mean serum PRL levels were significantly reduced (12 ± 3.1 ng/ml; p <0.001), a full normalization being obtained in 26 patients. There were no significant differences in both basal and after treatment PRL levels among patients treated with different drugs, although a greater PRL decrease was induced by cabergo-line. Serum OC levels significantly increased after 12 month therapy (4.7 ± 0.6 ng/ml, p <0.001), a normal concentration being reached in 14 of 29 cases. During treatment there were no significant differences in serum estradiol and PRL concentrations between patients who normalized or not their OC levels, while the reduction in PRL levels with respect to baseline was more pronounced in the former group. The absolute increase in OC levels positively correlated with serum PRL decrements (p <0.01). It is noteworthy that serum OC normalized in 1/10 patients during dihydroergocriptine, 3/8 during bromocriptine and 10/11 during cabergoline. Four patients, previously treated with dihydroergocriptine and bromocriptine without normalizing OC and PRL levels, underwent a second course of therapy with cabergoline and then normalized OC concentrations. In conclusion, these preliminary data show that i) OC levels are reduced in women with microprolactinoma, ii) after successful treatment of hyperprolactinemia a recovery of osteoblastic activity frequently occurs. Further investigations on the actions of dopaminergic drugs are needed, in view of their different effects on OC concentrations. Tresented in part at the 7th International Congress on calciotropic hormones and calcium metabolism, Salsomaggiore, Italy, October 1988.