Recent studies have emphasized the symbiotic role of estradiol and testosterone on bone metabolism. Several anthropomorphic-, lifestyle-, and dual-energy X-ray (DXA)-derived parameters were measured with respect to estradiol (E(2)), testosterone (T), free T (fT), and sex hormone-binding globulin (SHBG) in 140 men (aged 53-62 years) participating in a controlled, randomized exercise intervention trial. After 4 years of intervention, 132 (94.3%) men remained as participants. During the period of study, aerobic threshold increased significantly in the exercise intervention group compared with the reference group (13.4% vs. -1.9%: p < 0.023). Serum E(2) and fT were not convincingly related to bone mineral density (BMD) or BMD change. Aerobic threshold or the change in aerobic threshold were not associated with sex hormone or SHBG levels. Body mass index was a significant determinant of T (beta = -0.337), fT (beta = -0.293), and SHBG (beta = -0.306), and smoking predicted T (beta = 0.231) and fT (beta = 0.245). Alcohol intake was a significant determinant of E(2) (beta = 0.213). Ultimately there was no convincing relation between sex hormone levels and BMD or BMD change in middle-aged men.