BackgroundPrimary hyperparathyroidism (PHPT) with low preoperative vitamin D levels is thought to be related to 4-gland hyperplasia. We reviewed final parathyroid pathology in relationship to preoperative vitamin D levels. MethodsA retrospective review was performed for all PHPT patients undergoing parathyroidectomy from 2001 to 2019. Patient demographics, laboratory studies, and final pathology were reviewed. Results2230 patients were included in the analysis, 78.1% were female with a mean age of 59 years. Patients were stratified into 3 groups based on their preoperative 25-hydroxy vitamin D levels; “deficient” (<20 ng/mL) (n = 319), “insufficient” (20–30 ng/mL) (n = 1108), or “sufficient” (>30 ng/mL) (n = 803). Patients with deficient vitamin D had a higher frequency of single adenoma (71%) compared to sufficient vitamin D patients (62%) (p < 0.001) and fewer hyperplastic glands (19%) compared to sufficient vitamin D level patients (25%) (p < 0.001). ConclusionsVitamin D deficiency is more strongly associated with single-gland parathyroid disease than 4-gland hyperplasia. Further investigation into the complex interplay between vitamin D levels and autonomous parathyroid function is warranted.