Differential Diagnosis of Primary and Secondary Hyperparathyroidism Caused by Vitamin D Deficiency

Causes of secondary increase of parathyroid hormone, especially vitamin D deficiency, can significantly interfere with the diagnosis of hyperparathyroidism. The most difficult situation occurs when moderate increase in parathyroid hormone coincides with slightly elevated or normal levels of calcium in the blood serum. Given the predominantly surgical way of treating patients with primary hyperparathyroidism, it is important to distinguish vitamin D deficiency and indeed primary hyperparathyroidism. Objective: to develop a method for the differentiation of primary and secondary hyperparathyroidism associated with vitamin D deficiency. Materials and methods. We provide reliable, standardized protocol for short treatment with ergocalciferol (3000 IU a day for 45–50 days) to remove the effects of vitamin D deficiency on laboratory criteria of primary hyperparathyroidism. Reduction of more than 30 % and normalization of serum parathyroid hormone without serum calcium increase exclude primary hyperparathyroidism and the need for surgery. Results. We have studied a clinical group of 72 selected patients who meet the criteria of moderately elevated parathyroid hormone, normal or slightly increased levels of calcium, with vitamin D deficiency, absence of chronic kidney diseases or malabsorption. After 45–50 days of vitamin D intake, the normalization of parathyroid hormone without hypercalcaemia was observed in 61 patients (85 %). They were excluded from the clinical group of primary hyperparathyroidism. Hereafter, we did not observe cases of primary hyperparathyroidism progression in this group. The rest of the patients (10 of 72) were successfully operated for primary hyperparathyroidism, except one patient which refused surgery and is still under observation. Conclusions. Short ergocalciferol treatment can be a valuable and reliable clinical method to differentiate isolated vitamin D deficiency and asymptomatic primary hyperparathyroidism combined with a lack of vitamin D