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 primaryhyperparathyroidism (PHPt). DEsIGN: two patients (A and b) with PHPt took erroneously 2,400,000U (300,000 U/day for 8 days) and 4,500,000U (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.