Endocrine Abstracts

Introduction: Hypercalcemia associated with the use of a SGLT-2 inhibitor is a very rare adverse effect. Herein we reported a case of apparent primary hyperparathyroidism that occurred while applying the treatment of dapagliflozin in a patient with asymptomatic primary hyperparathyroidism.

Case report: A 49-year-old male patient with 5 years of diabetes mellitus history admitted for his routine control and Hba1c level was observed 7.9%. Dapagliflozin (1 × 10 mg) was started to the patient who has been using metformin (2 × 1000 mg) and gliclazide (1 × mg). At 6 months of dapagliflozin therapy, calcium level was detected 11.28 mg/dl, creatinine level was 1.21 mg/dl, and phosphorus level was 3.73 mg/dl, parathormone level was 70.8 ng/l, 25-(OH) vitamin D level was 33.16 ng/ml. A 4 × 9 × 14 mm-sized hypoechoic lesion located inferior to the right thyroid lobe, which was compatible with a parathyroid adenoma was detected on the neck ultrasonography. Because 99m-MIBI scintigraphy does not show an uptake compatible with parathyroid adenoma, four-dimensional computed tomography and magnetic resonance imaging were performed to clarify the localization of parathyroid adenoma. A 15 × 10 × 9-mm nodular lesion, which was compatible with the parathyroid adenoma was observed adjacent to lower part of the right thyroid gland. A 24-hours urine calcium level was 492 mg/day. The patient underwent lower right parathyroidectomy. Histopathological findings confirmed the diagnosis of parathyroid adenoma. After three months of the surgery, the patient is still asymptomatic and followed up with normal calcium levels.

Conclusion: Thiazide use and excessive calcium intake have been previously reported in the in the development of hypercalcemia while using SGLT-2 inhibitors. In response to increased absorption of phosphorus from the kidney, FGF-23 and parathormone levels increase. Another reason why SGLT-2 inhibitors cause moderate increase in calcium levels is the inhibition of both SGLT-1 and SGLT-2 receptors and the increase in calcium absorption in the intestines. Volume depletion caused by SGLT-2 inhibitors may also contribute to hypercalcemia. As the result of these mechanisms, calcium level may be seen increased with the use of SGLT-2 inhibitors. SGLT-2 inhibitors are medicines which lead to hypercalcemia and to reveal parathyroid adenoma that is not symptomatic. İt should be considered that calcium following-up might be needed while using SGLT-2 inhibitors.

Figure 1 Ultrasonographic appearance of the parathyroid adenoma.