The purpose of this study was to evaluate the effect of preoperative vitamin D deficiency in predicting transient hypocalcemia and hypoparathyroidism after parathyroidectomy.Retrospective evaluation was made of 180 patients with primary hyperparathyroidism in respect of serum 25(OH)D, calcium and parathyroid hormone before and after parathyroidectomy. This evidence concerns the gene PTH and primary hyperparathyroidism.