title: Primary hyperparathyroidism with low serum 1,25-dihydroxyvitamin D levels.
abstract: Primary hyperparathyroidism is usually associated with normal or elevated serum 1,25-dihydroxyvitamin D [1,25-(OH)2D] levels. We report a patient with extreme hypercalcemia (serum calcium, 19.4 mg/dl), primary hyperparathyroidism, and a very low plasma concentration of 1,25-(OH)2D. Surgical removal of a large parathyroid adenoma was associated with a decrease in the serum calcium and immuno- and bioactive PTH concentrations and normalization of the 1,25-(OH)2D level. The postoperative course was complicated by severe protracted hypocalcemia and cardiac arrest, requiring treatment with large doses of calcium iv. The low concentrations of 1,25-(OH)2D in this patient are an unusual manifestation of primary hyperparathyroidism, probably due to suppression of renal 1 alpha-hydroxylase activity by the severe hypercalcemia. We conclude that in severe hypercalcemia, a low serum 1,25-(OH)2D level does not exclude the diagnosis of primary hyperparathyroidism.
mesh_terms: D000236:Adenoma / Q000097:blood / Q000601:surgery; D000368:Aged; D002117:Calcitriol / Q000097:blood*; D002118:Calcium / Q000097:blood; D003404:Creatinine / Q000097:blood; D005260:Female; D006801:Humans; D006961:Hyperparathyroidism / Q000097:blood* / Q000601:surgery; D010282:Parathyroid Neoplasms / Q000097:blood / Q000601:surgery; D010710:Phosphates / Q000097:blood
chemical_list: D010710:Phosphates; D003404:Creatinine; D002117:Calcitriol; D002118:Calcium