Increase of bioavailable testosterone is associated with gain in bone mineral density after cure of primary hyperparathyroidism in postmenopausal women.

OBJECTIVE: The recovery of bone mineral density (BMD) after surgical cure of primary hyperparathyroidism (PHPT) seems to be multifactorial and not just dependent on declining PTH. The aim of the present study was to evaluate the role of sex steroids in this context.

DESIGN AND PATIENTS: Thirty-six postmenopausal women with PHPT were examined before and 1 year after curative parathyroidectomy. Their mean age at inclusion in the study was 71.7 +/- 1.1 years (range 54-83). BMD was measured in hip and lumbar spine using dual energy X-ray absorptiometry. No patient received any replacement therapy with sex hormones or treatment with corticosteroids, oestrogen receptor modulators or bisphosphonates.

MEASUREMENTS: Serum concentrations of oestradiol, testosterone, androstenedione, dehydroepiandrosterone sulphate, SHBG, PTH and calcium.

RESULTS: Postoperative increase of free (bioavailable) testosterone was positively correlated to the change of BMD in the hip (P < 0.01), whereas the change of PTH in serum correlated to the change of BMD in the lumbar spine (P < 0.05). Multiple regression analysis showed that bioavailable testosterone was the most important determinant of change in BMD in both spine and hip (femoral neck: P < 0.05; Ward's triangle: P < 0.001; trochanter: P < 0.01; lumbar spine: P < 0.05). The increase of bioavailable testosterone after curative parathyroidectomy was related to declining SHBG.

CONCLUSIONS: An increase of bioavailable testosterone following surgical cure of PHPT is related to improvement of hip and lumbar spine BMD in postmenopausal women. This previously unknown hormonal interaction may also be important to other aspects of hyperparathyroidism.