Calcium and phosphate metabolism in sarcoidosis with particular reference to parathyroid function

Fifty-six consecutive patients with sarcoidosis, 31 subacute and 25 chronic, were investigated for abnormalities of calcium and phosphate metabolism with particular reference to parathyroid function. No abnormality of serum calcium, phosphate, creatinine or alkaline phosphatase was found. Serum levels of 25-OH cholecalciferol were normal and parathyroid hormone levels were normal in all but one patient. Maximum renal tubular reabsorption capacities for calcium and phosphate (TmCa/GFR, TmP/GFR) in relation to glomerular filtration rate in the fasting state, were abnormal in some patients but this did not correlate with any other abnormality in parathyroid function. There was significant hypercalciuria (greater than 10 mmol calcium per 24 hours) in 7.5% of our patients and this is believed to be due to increased calcium flow.