Testosterone and testosterone free index in mild ankylosing spondylitis: relationship with bone mineral density and vertebral fractures.

OBJECTIVE: To determine the androgen status of men with mild ankylosing spondylitis (AS) and to evaluate the relationship of sex hormones with bone mineral density (BMD) and vertebral fractures. METHODS: Fifty-six male patients with mild AS were studied. All patients had BMD measured by dual x-ray absorptiometry (DXA) of the lumbar spine and hip, and had radiographs of the thoracic and lumbar spines. Radiographs were evaluated morphometrically, and vertebral fractures were defined using established criteria. Serum total testosterone, sex hormone binding globulin (SHBG), follicle stimulating hormone (FSH), and luteininzing hormone (LH) were measured in the patients with AS and 52 age matched controls. Testosterone free index (TFI) was calculated. RESULTS: There was a small, not significant reduction in serum total testosterone in patients with AS compared to controls [16.02 (5.0) vs 21.0 (6.2) nmol/l]. Serum SHBG was significantly lower in patients with AS [27.29 (10.6) vs 35.0 (13.0) nmol/l; p < 0.001] compared to controls. There was no significant difference in the mean TFI between patients and controls [58.7 (21.2) vs 60 (22.2) nmol/l; p > 0.05] or in the levels of LH and FSH. No significant correlation was found between sex hormones, BMD, and vertebral fractures in patients with AS. CONCLUSION: Sex hormones are not altered significantly in patients with mild AS and do not appear to be related to BMD or vertebral fractures. Osteopenia in men with mild AS is therefore unlikely to be secondary to hypogonadism.