Parathyroid Hormone as a Therapy for Idiopathic Osteoporosis in Men: Effects on Bone Mineral Density and Bone Markers

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Abstract
Osteoporosis in men poses a unique therapeutic challenge. Clinical studies have focused largely on the more prevalent problem of post- menopausal osteoporosis, with few gender-specific studies exploring treatment options in men. Idiopathic osteoporosis in middle-aged men presents an additional dilemma, because in the majority of patients it is a low bone turnover state for which there are currently no avail- able anabolic agents. We conducted an 18-month randomized, double blind, placebo- controlled trial of 23 men with idiopathic osteoporosis, 30 - 68 yr old (mean age 6 SEM ,5 06 1.9 yr). All patients received 1500 mg calcium and 400 IU vitamin D daily. Ten patients were randomized to receive 400 IU PTH-(1-34), and 13 patients received vehicle, administered by daily sc injection. Serum and urinary biochemistries, including mark- ers of bone turnover were measured every 3 months. Bone densitom- etry of the lumbar spine, hip, and radius was performed every 6 months. PTH-(1-34) was associated with a marked 13.5% increase in bone mass at the lumbar spine, whereas that in the control group did not change (P , 0.001). The mean lumbar spine T-score improved from 23.5 6 0.2 to 22.4 6 0.4. Femoral neck bone mineral density in the PTH-treated group increased 2.9% (P , 0.05). The 1/3 site of the distal radius showed no change from baseline in the PTH-treated group. There were no significant changes in serum calcium concentration, 24-h urinary calcium excretion, or 1,25-dihydroxyvitamin D in either group. All markers of bone turnover increased in the PTH-treated patients, with the greatest changes in serum osteocalcin and urinary N-telopeptide (230% and 375% above baseline by 12 months, respec- tively; P , 0.001). Free pyridinoline and markers of bone formation that showed little correlation with each other at baseline, became highly correlated in the PTH-treated group (r 5 0.1; P 5 0.29 at baseline; to r 5 0.7; P , 0.0001 at 18 months), a pattern absent in the control patients. The best predictor of the lumbar spine response to PTH at 18 months was the combination of pyridinoline at baseline and osteocalcin at 3 months (70% of the variance). PTH is a potent stimulator of skeletal dynamics in men with id- iopathic, low turnover osteoporosis; is associated with substantial increases in lumbar spine and hip bone density; and may prove to be an efficacious anabolic agent in men with this disorder. (J Clin En- docrinol Metab 85: 3069 -3076, 2000)

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