Secondary hyperparathyroidism is a condition in which the parathyroid glands become overactive due to an underlying medical condition. This overactivity leads to an increase in the production of parathyroid hormone (PTH), which can cause an increase in calcium levels in the blood. Common causes of secondary hyperparathyroidism include chronic kidney disease, vitamin D deficiency, and certain medications. Symptoms of secondary hyperparathyroidism may include fatigue, bone pain, and increased risk of fractures. Treatment typically involves addressing the underlying cause and may include medications, dietary changes, and/or surgery.