Age-related changes in bone metabolism are of interest in the pathogenesis of postmenopausal and senile osteoporosis; however, data in the literature give conflicting results. Thus, the aim of our study was to measure serum levels of osteocalcin, a specific biochemical parameter of bone formation, as well as serum levels of midregional parathyroid hormone (PTH) and alkaline phosphatase in healthy males and females of various age groups. We studied 155 healthy subjects (91 females, 64 males, mean age: 43 years, age range: 20-81 years). Serum levels of osteocalcin, alkaline phosphatase and PTH increased with age and were significantly higher in the postmenopausal than in the premenopausal females (osteocalcin: 8.7 +/- 0.4 vs. 6.5 +/- 0.3 ng/ml, p < 0.0001; alkaline phosphatase: 126 +/- 7 vs. 89 +/- 5 U/l, p < 0.0003; PTH: 111 +/- 10 vs. 61 +/- 9 pmol/l, p < 0.0001). In contrast, serum levels of osteocalcin, alkaline phosphatase and PTH were similar in the male subjects above or below the age of 50 years (osteocalcin: 6.5 +/- 0.5 vs. 7.2 +/- 0.4 ng/ml, non significant; alkaline phosphatase: 104 +/- 8 vs. 105 +/- 5 U/l, non significant; PTH: 59.6 +/- 6 vs. 61 +/- 5 pmol/l, non significant. Serum calcitonin levels were significantly lower in postmenopausal women and men above 50 years of age. Our data suggest different age-related alterations in bone metabolism in males and females. The increased levels of osteocalcin, alkaline phosphatase and PTH in postmenopausal females give evidence of increased bone turnover in these subjects. In healthy men bone-specific markers remained unchanged, indicating no relationship between bone turnover and age.