Hyperparathyroidism By James L Lewis III, MD, Brookwood Baptist Health and Saint Vincent's Ascension Health, Birmingham Reviewed / Revised Jan 2023 View Patient Education Etiology Pathophysiology Symptoms and Signs Diagnosis Treatment Key Points Hyperparathyroidism occurs when one or more of the parathyroid glands become overactive, causing elevated serum levels of parathyroid hormone and leading to hypercalcemia.