SAFETY OF VITAMIN D REPLACEMENT IN PATIENTS WITH PRIMARY HYPERPARATHYROIDISM AND CONCOMITANT VITAMIN D DEFICIENCY

Objective: To evaluate the safety of vitamin D replacement in patients with vitamin D deficiency and primary hyperparathyroidism. Methods: Retrospective chart review of 35 patients from our endocrine clinic, age 22 to 89 years, diagnosed with primary hyperparathyroidism and vitamin D deficiency, and treated with either 1,000 to 2,000 international units (IU) of vitamin D daily or 50,000 IU of vitamin D weekly for 5 months. Data were collected before and after treatment on serum calcium, 25-hydroxyvitamin D (25-OH D), intact parathyroid hormone (iPTH), phosphorus, alkaline phosphatase, nephrolithiasis, fractures, and osteoporosis. Results: 25-OH D increased significantly, from a baseline of 14.65 +/- 6.57 ng/mL to 42.17 +/- 12.98 ng/mL after weekly treatment with 50,000 IU of vitamin D (P<.0001), and from 22.42 +/- 5.47 ng/mL to 33.33 +/- 6.39 ng/mL following daily treatment with 1,000 to 2,000 IU of vitamin D (P<. 0001). Pre- and posttreatment unadjusted serum calcium remained stable in the high-dose group (10.80 +/- 0.43 mg/dL vs. 10.72 +/- 0.67 mg/dL; P = .47), but decreased slightly in the low-dose group (10.76 +/- 0.58 mg/dL vs. 10.11 +/- 0.54 mg/dL; P = .0007). After adjusting for age, sex, vitamin D, and PTH levels, the small calcium difference in the low-dose group became statistically insignificant. Treatment with either high or low doses of vitamin D did not significantly change iPTH levels. Creatinine remained stable in all patients, and no new cases of nephrolithiasis were reported. Conclusion: Replacing vitamin D in mild primary hyperparathyroidism is safe, effective, and does not increase calcium to dangerous levels.