The association between serum thyrotropin (TSH) levels and bone mineral density in healthy euthyroid men

Although osteoporosis is increasingly shown to occur in a considerable proportion of men, data on risk factors for male osteoporosis are limited. In this study, we investigated the association between serum thyrotropin (TSH) concentration and bone mineral density (BMD) in healthy euthyroid men. Design A cross-sectional community (health promotion centre)-based survey.

For 1478 apparently healthy euthyroid men who participated in a routine health screening examination, we measured BMD at the lumbar spine and femoral neck using dual energy X-ray absorptiometry and serum TSH concentrations using immunoluminometry.

Lumbar spine BMD linearly increased with TSH level after adjustment for age, weight and height (P for trend = 0.002), and statistical significance persisted after additional adjustment for smoking and drinking habits (P for trend = 0.010). When serum alkaline phosphatase was added as a confounding variable, the relationship was still significant (P for trend = 0.016). Femoral neck BMD also tended to increase in higher TSH concentration after adjustment for age, weight and height (P for trend = 0.042), but this association disappeared after additional adjustment for smoking and drinking habits. The odds of lower BMD (i.e. osteopaenia and osteoporosis combined) were significantly increased in subjects with low-normal TSH (i.e. 0.4-1.2 mU/l), when compared to high-normal TSH (i.e. 3.1-5.0 mU/l), after adjustment for confounding factors (odds ratio = 1.45, 95% CI = 1.02-2.10).

These results suggest that a serum TSH concentration at the lower end of the reference range may be associated with low BMD in men.