Calcium and phosphate metabolism in acromegaly

A study of 28 consecutively admitted patients with active acromegaly revealed the following results with regards to calcium and phosphate metabolism. When compared with controls, there was an increase in serum calcium levels corrected for total protein, urinary calcium was increased, but the tubular re-absorption of calcium was normal. There was a negative correlation between the urinary cAMP and calcium excretion indicating that hyperabsorption of calcium from the gut is the cause of the increased urinary calcium excretion. Serum phosphate values were increased in acromegalics and correlated well with TmP/GFR which was also increased. Immunoreactive parathyroid hormone (PTH) was increased in 5 patients, three of whom had hypercalcaemia. In the remaining patients the PTH values were scattered within the normal range. The urinary cAMP/creatinine ratio was increased in acromegalics, but most of this difference was abolished when urinary cAMP was expressed relative to 100 ml of glomerulus filtrate. It is concluded that parathyroid hyperactivity is a feature of acromegaly.