The role played by endogenous hormones in many diseases makes it important to understand factors influencing their levels. This study examined the distribution of total and free estradiol, FSH, and dehydroepiandrosterone sulfate (DHEAS) by age and sex and associations of these hormones with body mass index (BMI), lifestyle factors, and chronic diseases. Plasma samples taken from 1555 men and 1952 women 25-84 yr of age in 1994-1995 Tromsø Study were analyzed in 2001. Total estradiol increased with age among men (P < 0.001), with or without adjustment for BMI and lifestyle factors. FSH increased with age both in men (P < 0.001) as well as pre- (P < 0.001) and postmenopausal women (P = 0.01) after similar adjustment, and DHEAS decreased with age in both sexes (P < 0.001). With increasing BMI, free estradiol increased in men (P = 0.004), total and free estradiol increased in postmenopausal women (P < 0.001), and FSH decreased in men (P = 0.03) and postmenopausal women (P < 0.001). Men with chronic diseases had lower levels of DHEAS, compared with healthy men (P < 0.001). Smokers had higher DHEAS levels than nonsmokers. Further studies are needed to confirm these hormonal changes with age and disease.