Calcium homeostasis in morbid obesity

Calcium homeostasis in morbidly obese subjects has attracted little attention. Prompted by reports of elevated serum levels of parathyroid hormone in such patients, calcium homeostasis was investigated in 36 patients with morbid obesity and in 44 normal weight controls. Concerning serum immunoreactive parathyroid hormone (C-terminal), serum ionized calcium (Ca++) and serum albumin corrected magnesium no significant differences between the groups were detected. When albumin corrected, serum total calcium turned out to be significantly elevated (p less than 0.0001) in the obese subjects. Also, serum alkaline phosphatase activity was significantly raised in the obese state. The results demonstrate that calcium homeostasis, as expressed by the metabolically active serum Ca++, is normal in morbid obesity. But the results also point towards an abnormal calcium binding due to either an increased calcium binding to albumin or to calcium complexing small anions.