IGF‐I and testosterone levels as predictors of bone mineral density in healthy, community‐dwelling men

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Abstract
Objective Age‐related decline in IGF‐I and gonadal hormones have been postulated to play an important role in the pathogenesis of age‐related bone loss in men. In this cross‐sectional study, the relation between serum IGF‐I and gonadal hormones with bone mineral density (BMD) was examined in community‐dwelling men. design and subjects Serum IGF‐I, testosterone and BMD were examined in 61 community‐dwelling men over the age of 27, who were randomly selected from the Calgary cohort of 1000 subjects in the Canadian Multicentre Osteoporosis Study. In the present study, IGF‐I, serum testosterone, SHBG, free androgen index (FAI), parathyroid hormone (PTH), 25‐hydroxy‐vitamin D [25(OH)D] and other markers of bone turnover were measured. BMD was measured at the spine and hip (HOLOGIC 4500). Simple linear regression was used to assess the linear relation between IGF‐I, testosterone, BMD and other biochemical markers of bone metabolism and potential confounding variables and subsequent multivariate regression models were constructed separately for each BMD measurement to assess the importance of IGF‐I and testosterone in the presence of potential confounding variables. results Serum IGF‐I, FAI and SHBG significantly decreased as a function of age, whereas serum levels of PTH increased. Only 25(OH)D, total testosterone and FAI were positively associated with serum IGF‐I after adjusting for age and BMI. Multiple linear regression models revealed that IGF‐I was a significant predictor of BMD at the total hip, femoral neck and femoral trochanter neck (P ≤ 0·001). In contrast, the FAI was a significant predictor of BMD at the lumbar spine and wards area (P ≤ 0·011), and SHBG was a significant predictor at the total hip and femoral trochanter (P ≤ 0·045). conclusion These data support the hypothesis that the age‐related decline in bone mass in men is associated with declining levels of IGF‐I and testosterone.