ABSTRACT
The level of circulating calcitonin was followed up in 30 patients with severe hypothyroidism, diagnosed clinically and by laboratory examinations. Four of the patients under study had goiter. The complex investigation of phosphorus-calcium metabolism, including radioimmunoassay of calcitonin was made under basal conditions and after calcium loading. The results revealed low basal urinary calcium excretion and an increased skeletal uptake of calcium after loading. Calcitonin secretion persisted in 8 of the patients under basal conditions and it increased after calcium loading in another 14 of them, accounting for the increased "skeletal avidity" for calcium. The persistence of calcitonin secretion supports an earlier clinical observation concerning the relative integrity of the skeleton in patients with hypothyroidism. In the hypothyroid patients with goiter the results do not differ from those obtained in the remaining patients.
