Abstract

Sarah Exley LPN, Hannah Porter DO and Udaya M. Kabadi MD*

ABSTRACT

Individuals presenting with elevated PTH, normal serum calcium and subnormal Vitamin D may not all have secondary hyperparathyroidism due to Vitamin D deficiency. Enhanced conversion of 25-hydroxyvitamin D3 (25OHD) into 1,25-dihdroxyvitamin D3 (1,25OHD) in primary hyperparathyroidism has been seen in previous studies. The purpose of this study is to assess the effect of Vitamin D supplementation on serum PTH, calcium and 25OHD concentrations in subjects manifesting subnormal Vitamin D, normal serum calcium and elevated PTH levels. Results: Results showed that participants fell into one of two groups; 1.) PTH lowering (95 ± 12 to 48 ± 6, p<0.01) in response to normalization of 25OHD levels without significantly impacting serum Calcium. 2.) Lack of PTH response to normalization of 25OHD levels and an increase in serum Calcium (9.6 ± 0.4 to 11.1 ± 0.4, p < 0.01). Conclusion: Subjects manifesting low 25 OH Vitamin D, normal calcium and elevated PTH concentrations belong to two groups; 1.) Vitamin D deficiency with secondary hyperparathyroidism; 2.) Normocalcemic primary hyperparathyroidism with low 25 OH Vit D levels secondary to enhanced conversion to 125 OH Vitamin D, documented previously in hypercalcemic primary hyperparathyroidism.