We tested the hypothesis that biomarkers of bone resorption are increased in hyperprolactinemic amenorrheic patients with estrogen (E) deficiency, augmenting the possible risk of developing osteoporosis. Fifty hyperprolactinemic patients with amenorrhea of more than 12 months and with low serum E2, as well as 30 healthy fertile women (controls), matched for age and body mass index, participated in this study. Bromocriptine was administered orally to hyperprolactinemic patients and blood and urine samples were collected before and 12 weeks after treatment. Serum osteocalcin (OC) and bone-specific alkaline phosphatase (B-ALP), reflecting bone formation, and urinary deoxypridinoline (D-Pyr) and N-telopeptide of type 1 collagen (NTX) excretion, reflecting bone resorption, were measured using direct immunoassays. Hyperprolactinemic patients had higher (p < 0.0005) levels of all the biomarkers compared to control values: (OC, 22 ± 1.2 [SE] vs. 14 ± 0.99 ng/ml (+57 %); B-ALP, 14.2 ± 0.7 vs. 7.5 ± 0.8 ng/ml (+89 %); D-Pyr, 8.8 ± 0.6 vs. 3.2 ± 0.3 nmol/mmol creatinine (+175 %) and NTX, 65 ± 5.1 vs. 25 ± 3.2 nmol bone collagen equivalent (BCE)/mmol creatinine (+160 %)). These results were associated with significantly decreased lumbar spine bone mineral density (LS-BMD), measured by dual energy X-ray absorptiometry (DEXA). Treatment of hyperprolactinemia with bromocriptine restored normal values of bone formation and resorption markers. In conclusion, hyperprolactinemia with estrogen deficiency exhibits a significant increase of bone resorption which is associated with a significant decrease of LS-BMD. These changes may subject the patient to the possible risk of developing osteoporosis.
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