Sex hormone status and bone metabolism in men with Crohn's disease

Men with Crohn's disease (CD) are at risk of osteoporosis, but the factors contributing to low bone mineral density and its optimum treatment have not been established.

To investigate the sex hormone status of men with CD, and to establish the influence of sex hormones on their bone metabolism.

Bone density was measured by dual energy X-ray absorptiometry at the hip and lumbar spine in 48 men with CD. Total serum testosterone and gonadotrophins were measured in all subjects and the free androgen index calculated in men with low or borderline total testosterone. Serum osteocalcin, pro-collagen carboxy-terminal peptide, bone specific alkaline phosphatase and urinary deoxypyridinoline were measured as markers of bone turnover.

Eight (17%) men had osteoporosis, and a further 14 (29%) had osteopenia. Three (6%) men had a low free androgen index and normal gonadotrophins consistent with secondary hypogonadism, two of whom had osteopenia of the hip and spine. Age (P = 0.002) and small bowel Crohn's disease (P = 0.02) were the only independent predictors of serum testosterone. There was a significant association between total testosterone and osteocalcin (r = 0.53, 95%, CI: 0.29-0.71, P = 0.0001) which was independent of age and current steroid use (P = 0.0001).

Previously undiagnosed hypogonadism is an uncommon cause of low bone density in men with CD. The independent association between testosterone and the bone formation marker osteocalcin suggests sex hormone status influences bone metabolism in men with CD. The results suggest testosterone replacement might be effective treatment for some men with osteoporosis and Crohn's disease.