Unmasking of Normocalcemic Primary Hyperparathyroidism After Sodium-Glucose Cotransporter-2 Inhibitor Initiation.

Sodium-glucose cotransporter-2 (SGLT2) inhibitors have complex interactions with bone metabolism, including an increase in parathyroid hormone (PTH) levels. Here we report a case of a SGLT2 inhibitor-induced hypercalcemia due to primary hyperparathyroidism. In the subset of patients with normocalcemic primary hyperparathyroidism, SGLT2 inhibitor initiation can unmask the disorder causing overt hypercalcaemic hyperparathyroidism. Although normocalcemic primary hyperparathyroidism is a rare entity, we propose obtaining a baseline PTH level before starting a SGLT2 inhibitor in patients with calcium levels in the upper limit of normal and normal total 25-hydroxyvitamin D levels, especially if they are under vitamin D supplementation. PTH should be rechecked in order to exclude overt primary hyperparathyroidism. LEARNING POINTS: Sodium-glucose cotransporter-2 (SGLT2) inhibitors are a class of medications that cause secondary hyperparathyroidism.In patients with normocalcemic primary hyperparathyroidism, SGLT2 inhibitor' initiation can cause overt hyperparathyroidism and hypercalcemia.We propose obtaining a baseline parathyroid hormone level before starting a SGLT2 inhibitor in patients with calcium levels in the upper limit of normal especially if they are under vitamin D supplementation.