Osteoporosis and Klinefelter's syndrome.

OBJECTIVE: We wanted to measure forearm mineral density and bone-related biochemical variables in patients with Klinefelter's syndrome.

DESIGN: Measurements made in patients with Klinefelter's syndrome were compared to those obtained in age-matched normal male volunteers.

PATIENTS: We studied 22 patients with Klinefelter's syndrome (12 of whom had received sex hormone therapy) and 22 control subjects.

MEASUREMENTS: We measured forearm mineral density, forearm fat content, fat-corrected forearm mineral density, plasma calcium and ionized calcium, serum osteocalcin, testosterone and dehydroepiandrosterone sulphate, and urinary hydroxyproline/creatinine ratio.

RESULTS: Forearm mineral density was lower in the Klinefelter's group than in the control subjects (P less than 0.05) and below the control range in 5 patients. The fat content of the forearm was greater in the Klinefelter's group (P less than 0.002). Serum osteocalcin and testosterone were lower, while ionized calcium and the urinary hydroxyproline/creatinine ratio were higher in the Klinefelter's group (P less than 0.002). Serum dehydroepiandrosterone sulphate and testosterone were significantly related in the Klinefelter's group (r = 0.64, P less than 0.001), but not in the controls (r = 0.22, NS). Forearm mineral density and fat-corrected forearm mineral density were significantly related to serum testosterone in the Klinefelter's group (r less than 0.63; P less than 0.01), but not in the control subjects (r less than 0.03, NS).

CONCLUSIONS: Decreased bone density occurs in about 25% of patients with Klinefelter's syndrome and probably reflects both decreased bone formation and increased bone resorption.