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.