Calcium and Phosphate Homeostasis and Bone Mineral Density Changes after Withdrawal of Oral Calcium Carbonate in Hypoparathyroidism: A Seven-Year Follow-up
Soma Saha, Ravinder GoswamiAbstract
Introduction:
Vitamin D and oral calcium constitute the conventional therapy in chronic hypoparathyroidism (cHypoPT). Oral calcium carbonate (CaCO 3 ) binds dietary phosphate in the intestine and might reduce serum phosphate. The role of CaCO 3 on calcium and phosphate homeostasis, bone mineral density (BMD) and renal calcification is not known.
Methods:
Subjects were 39 cHypoPT patients (male:female = 17:22; age 49.4 ± 15.2 years; duration of illness 22.8 ± 9.3 years) who had participated earlier in a 2017–2018 study evaluating the efficacy of conventional therapy. All patients received alfacalcidol. However, 17 were managed without oral CaCO 3 (group 1). Twelve patients were managed with 1.0 g of CaCO 3 /day (group 2). In 10 patients, oral CaCO 3 was continued at a dose of 2.0 g/day (group 3). Their serum total calcium, phosphate, fractional excretion of phosphate (FEPh), 24-h urine calcium/creatinine, estimated glomerular filtration rate (eGFR), renal calcifications and BMD were compared before and after 7 years of CaCO 3 withdrawal.
Results:
The mean serum total calcium was in the optimal range during follow-up in all groups. Although mean serum phosphate showed no significant change in the three groups, FEPh increased (10.85 ± 4.78% to 17.87 ± 10.61%,
Conclusions:
Patients with cHypoPT could maintain long-term optimal calcaemic control without oral CaCO 3 . Though withdrawal of CaCO 3 did not increase serum phosphate, it led to increased phosphaturia and possible renal calcification. The elevated BMD in cHypoPT with longer duration of conventional therapy did not occur in patients who were completely off oral CaCO 3 .