Bone mass in middle-aged osteoporotic men and their relatives: familial effect

Severe idiopathic osteoporosis in middle-aged men is still poorly understood. The aim of this study was to assess the contribution of genetic factors in these patients. We studied 38 men (mean age +/- SD, 50 +/- 11 years) presenting with vertebral or peripheral bone fractures due to primary osteoporosis and 73 of their relatives divided into four subgroups: 19 brothers, 22 sisters, 13 sons, and 19 daughters. The control group comprised 199 age-matched subjects. In all subjects, we measured bone mineral density (BMD) and calculated the Z score at the lumbar spine (LS) and femoral neck (FN) based on the fitted BMD value in the controls. LS BMD values were lower in each of the four subgroups compared with the age-matched controls. The mean Z score for the overall group of 73 relatives was decreased compared with the age-matched controls (-1. 28 +/- 1.48 at the LS and -1.03 +/- 1.19 at the FN) and was not influenced by gender or by whether the relatives were siblings or children. An LS Z score < -1) was found in 54.8% of the relatives of osteoporotic patients versus 17.4% of the control subjects (risk ratio, 3.2). Alcohol and tobacco abuse are well-known risk factors for osteoporosis in men. Among the 38 osteoporotic patients, 7 were heavy smokers (>20 pack-years), 8 were both heavy smokers and drinkers (>80 g/day for at least 10 years and gammaGT > 40 UI/l), and 23 had neither of these risk factors. BMD, Z score, and anthropometric data were the same in patients with and without risk factors. Decreases in LS and FN Z scores were similar in relatives of patients with and without risk factors. In conclusion, low BMD is observed in relatives of osteoporotic men with or without risk factors for osteoporosis, indicating that familial factors contribute to primary osteoporosis in middle-aged men.