Long-term measurement of skeletal and lean body mass in Paget's disease of bone treated with synthetic human calcitonin.

Total body calcium (an index of skeletal mass), ulnar bone density, and total body potassium (lean body mass) were followed for up to 5 years in 38 patients with Paget's disease during treatment with synthetic human calcitonin. Calcium was measured by neutron activation, ulnar density by X-ray photodensitometry, and potassium by counting its natural 40K radioactivity. There was a significant rise in total skeletal mass in a group of 8 patients in the 12 months following the start of therapy, but overall, total bone mass and ulnar density remained constant during treatment. Small mean losses of body potassium were observed (approximately 4%) after several years elapsed on treatment. Over an average period of 12 months after discontinuation of therapy in 21 patients there was no significant mean change in calcium or potassium. The means of the ratios of total body calcium divided by predicted normal calcium (over the whole period of measurement) were 1.08 (males) and 0.99 (females) and were not significantly different. Comparison of the ulnar densities of patients and normal subjects gave similar results. The average ratio of measured to predicted normal potassium was 1.13 (both males and females). Thus there was no indication of depletion in skeletal mass below normal either in the untreated disease or resulting from treatment.