Alterations of calcium and phosphate metabolism in primary hyperparathyroidism during pregnancy

Abstract

Primary hyperparathyroidism (PHP) is rare during pregnancy and has been claimed to be associated with significant increase of neonatal morbidity and mortality. Whether the well recognized changes in calcium (Ca) and phosphate (Pi) homeostasis occurring in pregnancy might influence the biochemical expression of PHP is unclear. We evaluated biochemical parameters of calcium and phosphate metabolism in two cases of PHP in pregnancy diagnosed in the third trimester (patient 1) and in the second trimester (patient 2). Both patients displayed increase in protein-adjusted plasma Ca, bone resorption evaluated by the fasting urinary Ca-to-creatinine ratio, renal tubular reabsorption of Ca, urinary cAMP excretion and decrease in renal tubular reabsorption of Pi. These alterations were identical to those found in 12 non-pregnant women with PHP. The biochemical expression of PHP did not change after delivery in patient 1. This patient underwent the excision of a 1 g parathyroid adenoma on the 13th day after delivery, which led to normalization of all biochemical parameters. The lowest plasma Ca of the newborn of patient 1 was 2.02 mM 72 hours after birth. Thus, the results indicate that these two pregnant women with PHP displayed biochemical alterations of calcium and phosphate metabolism similar to those observed in non-pregnant women with primary hyperparathyroidism.