Alternate-day calcium dosing may be an effective treatment option for chronic hypoparathyroidism

Purpose Conventional treatment of chronic hypoparathyroidism consists of oral calcium supplements and active vitamin D analogs; however, some patients are unable to meet treatment goals despite the high dosage of oral calcium supplementation. We aimed to investigate the effectiveness of alternate-day oral calcium intake in patients with uncontrolled chronic hypoparathyroidism. Methods In this retrospective cohort study, we evaluated 66 patients with chronic hypoparathyroidism who were admitted to our hospital between January 2017 and January 2019. Fourteen patients receiving ≥ 2000 mg/day oral elemental calcium and who were admitted to emergency department or our outpatient clinic at least once in the last 3 months for hypocalcemia requiring intravenous calcium replacement were switched to the alternate-day dosing regimen in which patients took calcium orally every other day. We collected and analyzed patients’ medical history information, serum and urinary parameters over a 3-month period prior to and following the treatment. Results Before alternate-day dosing regimen, median oral calcium intake was 3750 mg/day, oral calcitriol intake was 0.88 mcg/day, serum calcium levels were 7.71 mg/dL, serum phosphate levels were 5.35 mg/dL, and 24-h urine calcium levels were 165 mg/day. Following alternate-day dosing regimen, median oral calcium intake was 1500 mg/day, oral calcitriol intake was 0.88 mcg/day, serum calcium levels were 8.25 mg/dL, serum phosphate levels were 5 mg/dL, and 24-h urine calcium levels were 210.5 mg/day. After alternate-day dosing regimen, oral calcium intake decreased and serum calcium levels increased. The number of emergency visits dropped from 21 to 3 after alternate-day dosing regimen. Conclusion Patients with uncontrolled chronic hypoparathyroidism could be controlled more effectively with alternate-day dosing regimen.