Low
vitamin D levels have been shown to be associated with
primary hyperparathyroidism, but it is unclear whether
vitamin D deficiency may be an etiologic factor in the development of
primary hyperparathyroidism. To investigate this, we compared preoperative
vitamin D levels of patients undergoing surgery for
primary hyperparathyroidism with those of patients undergoing surgery for benign
thyroid disease. With Institutional Review Board approval, data were collected prospectively on patients undergoing
parathyroidectomy or
thyroidectomy by one surgeon between March 2006 and July 2011. Patients were excluded if they underwent simultaneous thyroid and parathyroid surgery, had secondary or tertiary
hyperparathyroidism, if no preoperative
vitamin D level was measured, or if they took
vitamin D supplements. Inclusion criteria were met by 219 patients who underwent
parathyroidectomy and 186 patients who underwent thyroid surgery. Patient age, sex, race, and preoperative
vitamin D levels (
vitamin D 25-
OH; normal, 32 to 100 pg/mL) were collected. Statistical analysis was performed using linear regression.
Vitamin D levels were significantly lower in the parathyroid group compared with the thyroid group (23.8 vs 28.5 pg/mL; P < 0.001). This difference was also observed after adjustment for age, sex, and race with a mean difference of 4.87 pg/mL (P < 0.001). Statistically significant associations between lower
vitamin D levels and patients younger than 50 years (P = 0.048), male sex (P = 0.03), and nonwhite race were identified (P < 0.001). Patients with
primary hyperparathyroidism are more likely to have lower
vitamin D levels than a control surgical population. Further study is needed to determine whether low
vitamin D levels may be an etiologic factor associated with the development of
hyperparathyroidism.