Insulin-like growth factor-1 and free testosterone as early serum markers of osteoporosis in elderly men

Objectives: Osteoporosis is rare in men, affecting almost exclusively the elderly, while up to 30% of postmenopausal women may have low bone density (BMD). In both sexes, dual-energy X-ray absorptiometry (DXA) is usually considered a reliable tool to evaluate bone loss by nearing BMD. However, several potential serum markers of bone remodeling, including insulin-like growth factor (IGF)-1 and free testosterone (FT) have been investigated, not only in order to identify bone changes early, but also to predict subsequent losses in BMD and prevent the risk of some adverse skeletal-related events. The aim of this study was to evaluate the relationship between BMD, serum OGF-1, and FT in a group of osteoporotic men older than 65 years with DXA-confirmed osteoporosis. Methods: We retrospectively reviewed the medical records of 17 elderly men (median age 69 years, range 66-76) who underwent DXA (Hologic QDR 4500 C, Waltham. MA, USA) and lumbar spine (L2-L4) BMD measurement. Serum OGF-1 was measured by an immunichemiluminescent (ICMA) method (Maglumi 2000, SNIBE, China), while serum FT was assayed by a radioimmunoassay (RIA) method (Immunotech, Prague, Czech Republic). Results: The results were the following: LS-BMD=0.760±0.064 g/cm2; IGF-1=10.7±26.3 mcg/L; FT=277.6±33.5 pmol/L. No correlation was found between BMD and the age of the patients (R=-0.28, p=0.27), BMD (R=0.01, p=0.96), PTH (R=0.02, p=0.93), and 25-hydroxyvitamin D (R=0.13, p=0.61). The regression linear equations between BMD, IGF-1, and FT were BMD=3.404-120.389IGF-1 (R=0.82, p<0.001), and BMD=504.601-2.959FT (R=-0.56, p=0.017). No significant relationship between IGF-1 and FT (R=0.33, p=0.19) was found. Conclusion: High IGF-1 and low FT serum levels are independently related to low BMD, suggesting that the two markers together could be used in the early diagnosis of bone loss in elderly men. Further studies will eventually confirm our results.