Primary Hyperparathyroidism Corrected by Vitamin D supplementation: A Rare Presentation

ABSTRACT

Introduction: Primary hyperparathyroidism (PHTP) is a common endocrine disorder characterized by high parathyroid hormone (PTH) and calcium levels, commonly detected incidentally. A common concurrent finding is vitamin D deficiency, with a reported incidence of as high 91%. Vitamin D administration in PHPT is controversial due to a risk of exacerbating hypercalcemia, though some studies have shown that this may in fact be beneficial by suppressing PTH levels and decreasing bone demineralization. We present an interesting case of a 45-year-old male presenting with asymptomatic PHPT which was successfully managed solely with vitamin D administration. Case Description Our patient is a 45-year-old male who was seen for an incidentally detected elevated calcium level of 10.4 mg/dl and a PTH level of 146.3 pg/ml. The patient denied a history of nephrolithiasis, polyuria, bone pain, or other hypercalcemia symptoms. A Computed Tomography scan of his neck followed by a Single Proton Emission Computerized Tomography (SPECT) demonstrated a potential right sided parathyroid adenoma. The rest of his workup was notable only for a severely decreased vitamin D level of 10.7 ng/ml. Although he qualified for surgical intervention based on his age, a decision regarding surgery was deferred because of the COVID pandemic. Vitamin D supplementation was started at 1000 units daily. Subsequent labs showed an initial increase in PTH to 189 pg/ml, later trending down to 155 pg/ml after his vitamin D dose was increased from 1000 U to 5000 U at 3 months. At 6 months, both PTH and calcium levels showed significant improvement coming down to 80 ng/ml and 9.3 mg/dl, respectively, in concert with improving Vitamin D levels. Discussion: Vitamin D deficiency often coexists with PHPT and is associated with both more severe disease and worse outcomes after parathyroidectomy. Correction of vitamin D deficiency in PHPT is controversial and is feared to worsen underlying hypercalcemia. Two meta-analyses, done in 2014 and 2021, have however demonstrated that vitamin D supplementation can be safely used and lowers PTH levels without causing hypercalcemia or hypercalciuria. Potentially, this could be due to a reduction in bone turnover due to the reduction in PTH, though at present this remains an area for further study. Our case represents only the second reported case of a patient with PHPT who, when treated with vitamin D, showed improvement in both hypercalcemia and PTH levels. Therefore, we postulate that it may be reasonable to defer the decision about surgery in asymptomatic patients with PHPT and concurrent vitamin D deficiency until after the vitamin D deficiency has been corrected.