Over-supplementation of vitamin D in two patients with primary hyperparathyroidism.

Objective: To describe the biochemical effects of an over-supplementation of vitamin D3 in two patients with primary hyperparathyroidism (PHPT).
Design: Two patients (A and B) with PHPT took erroneously 2,400,000 U (300,000 U/day for 8 days) and 4,500,000 U (300,000 U/day for 15 days) of cholecalciferol, respectively. They were followed for 4 months and ionized calcium, creatinine, PTH, 25 hydroxy-vitamin D, 1,25(OH)₂D and urinary calcium/creatinine levels were measured. Finally, the patients were operated on and a parathyroid adenoma was removed in both.
Results: One week after the last dose of vitamin D, serum ionized calcium (iCa) rose from 1.35 to 1.41 mMol/L (n.r. 1.14-1.31) for patient A, and from 1.43 to 1.62 for patient B, while fasting urinary Calcium/Creatinine (uCa/Cr) augmented from 0.31 to 0.50 mg/mg, and from 0.32 to 0.55, respectively. During the follow-up, the average levels of iCa were 1.37 ± 0.03 and 1.48 ± 0.07 mMol/L, while those of uCa/Cr were 0.29 ± 0.13 and 0.32 ± 0.13, both iCa and uCa/Cr levels returning to baseline values within 4 months.
Conclusions: The unintentional over-supplementation of vitamin D in the two PHPT patients caused a moderate and temporary increase of hypercalcemia and hypercalciuria and was not associated with clinical signs of toxicity.