Searchable abstracts of presentations at key conferences in endocrinology
Endocrine Abstracts (2015) 37 EP314 | DOI: 10.1530/endoabs.37.EP314

ECE2015 Eposter Presentations Calcium and Vitamin D metabolism (96 abstracts)

Idiopathic hypercalcaemia in pregnancy not due to PTHrP: suggestion for another pathomechanism by genetic defect of 24-hydroxylase

Csaba Horvath 1 , Szilvia Meszaros 1 , Orsolya Acs 2 , Eva Hosszu 2 , Julia Nemeth 3 , Emoke Csupor 4 , Miklos Szathmari 1 , Nandor Acs 5 & Eugene V McCloskey 6

11st Department of Internal Medicine, Semmelweis University, Budapest, Hungary; 22nd Department of Pediatrics, Semmelweis University, Budapest, Hungary; 3Synlab Hungary, Budaors, Hungary; 4Budavar Endocrine Center, Budapest, Hungary; 52nd Department of Obstetrics and Gynecology, Semmelweis University, Budapest, Hungary; 6Centre for Metabolic Bone Diseases, Sheffield University, Sheffield, UK.

A 32-year-old women initially presented with recurrent kidney stones and was found to have nephrocalcinosis. She was found to normocalcaemic but hypercalciuric, with a plasma ionized calcium at upper-limit of normal and a PTH in lower normal range. One year later, during the first trimester of a pregnancy, she presented with severe hypercalcaemia, hypercalciuria and suppression of PTH. Extensive investigations for causes of hypercalcaemia excluded hyperparathyroidism, other endocrine diseases, hematologic or other malignancies, granuomatous diseases, renal tubular acidosis and milk-alkali syndrome. Plasma PTHrP was suppressed. She had not taken any form of vitamin D, however, her serum level of 25OHD3 was normal throughout the pregnancy (even in wintertime) and the serum level of 1,25(OH)2D was elevated. Continuous high oral and parenteral fluid intake resulted in a moderate decrease of hypercalcaemia and no change in hypercalciuria. At 35 weeks a healthy boy was born with a transient hypercalcaemia that normalized spontaneously within a few days. The maternal hypercalcaemia decreased but remained above reference range with continuing suppression of PTH. Disturbed vitamin D metabolism, especially a reduction in 24-hydroxylation by genetic mutations has been observed in familial cases of nephrocalcinosis and in infants with idiopathic hypercalcaemia after usual doses of vitamin D supplementation. We hypothesise that our patient had an insufficient 24-hydroxylation in the kidney and it has been intensified during pregnancy by the placenta as a well-known site of vitamin D activation for local immune purposes. If this is the case, then our patient could be the first one in whom the defective 24-hydroxylation produces hypercalcaemia without provocative effect of external vitamin D stimulation. To prove this hypothesis, the genetic analysis of mutations in CYP24A1 gene will be performed.

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