Hypercalcemia in hyperthyroidism. Role of age and goiter type.

Hyperthyroidism is often associated with hypercalcemia which is provoked by osteoclastic activity of the thyroid hormones. These data show that hypercalcemia develops with increasing age and in the presence of a special type of hyperthyroid goiter. Total serum calcium, total protein, and albumin as well as different parameters of thyroid function, namely T3 RIA1, T4 test, ETR and TRH test were determined in a group of 147 patients. The ionized calcium level was estimated from total calcium and albumin. 211 measurements were performed. Hyperthyroidism existed in 92 cases. Total calcium was not significantly elevated in hyperthyroidism. Hyperthyroid patients under 61 years of age showed elevated ionized calcium levels in only 2.3% and patients over 60 years of age in 18.8% of cases. Elevated ionized serum calcium levels were observed in 43.8% of hyperthyroid patients with multinodular goiters. The linear correlation between ionized calcium levels and different parameters of thyroid function is much more pronounced in the older group and it was found to be highly significant. 7 of 9 hyperthyroid patients with elevated ionized calcium levels showed multinodular goiters, though no autonomous adenoma. In the hyperthyroid group of patients of over 60 years of age with multinodular goiters the incidence of hypercalcemia was 43.8%. Direct action of thyroid hormone on calcium turnover as well as increasing age and special goiter type seem to be responsible for disturbances in calcium metabolism. A possible calcitonin deficiency in the above mentioned conditions is discussed.