Plasma Calcitonin in Normal Man

Abstract

We measured plasma calcitonin concentrations in healthy volunteers (20 men, ages 23-45 yr, mean, 30 yr; 25 women, ages 21-46 yr, mean, 30 yr) with a radioimmunoassay capable of detecting 5 pg of calcitonin/500 μl incubation volume, or 25 pg/ml of unextracted plasma. All subjects had 4-h calcium infusion (15 mg Ca/kg), and 24 subjects had intravenous pentagastrin injection (0.5 μg/kg) on separate days. Men had higher basal plasma immunoreactive calcitonin concentrations than women (P < 0.001): mean, 49 pg/ml (range, P < 0.02; pentagastrin, P < 0.001). The physiologic importance of these observations is unknown, but we speculate that a lifelong, relative deficiency of calcitonin in some women could play a role in age- and sex-related bone loss, particularly during the estrogen-deficient postmenopausal years.