It has been suggested that postmenopausal osteoporosis is due to calcitonin deficiency. Interest in this concept has been increased because of the recent availability of nasal calcitonin for the management of osteoporosis. Plasma calcitonin and albumin-adjusted calcium levels were measured in 30 women with postmenopausal osteoporosis and 41 normal women matched for age and sex. Both mean plasma calcitonin and mean albumin-adjusted calcium levels were higher in the postmenopausal osteoporotic women [calcitonin, 21.0 +/- 17.6 (+/- SD) vs. 9.8 +/- 10.2 ng/L (P = 0.003); calcium, 2.33 +/- 0.09 vs. 2.27 +/- 0.07 mmol/L (P = 0.002)]. This result indicates that fasting calcitonin deficiency is not a feature of postmenopausal osteoporosis.