Endocrine Abstracts

Introduction: Hypoparathyroidism is characterized by hypocalcemia and low or inappropriately normal levels of PTH. The most common cause of hypoparathyroidism is iatrogenic due to anterior neck surgery. In recent years it was documented that vitamin D insufficiency is widespread.

Aim: To investigate the cause of hypocalcemia in thyroidectomized patients with PTH within the reference range.

Methods: Retrospective review of clinical records of patients who underwent thyroid surgery with hypocalcemia and PTH within reference values. PTH was measured by chemiluminescent immunoassay (Immulite 2000) with reference values between 11 and 65 pg/ml and 25-OH-vitamin D was dosed by electrochemiluminescence (Cobas e411) with reference values between 30 and 100 ng/ml.

Results: We evaluated 16 patients (88% female) with a mean age (±S.D.) of 42±14 years at the time of surgery. On postoperative evaluations, all of them had ‘normal’ PTH values with hypocalcemia, in which 11 needed calcium and/or calcitriol. Hypovitaminosis D was documented in 13 of 14 patients (93%) in which this parameter was assessed, of whom three had vitamin D <10 ng/ml (deficiency) and ten had vitamin D between 10–30 ng/ml (insufficiency). In two patients vitamin D was not dosed. One patient had sufficient vitamin D (>30 ng/ml).

Discussion/conclusion: A normal PTH value does not exclude the presence of postsurgical hypoparathyroidism. Lack of vitamin D in patients with impaired parathyroid reserve may explain the hypocalcemia. These situations could probably benefit from treatment with colecalciferol.