Cinacalcet is primarily used in the treatment of secondary hyperparathyroidism in patients with chronic kidney disease who are on dialysis. It helps to regulate calcium levels in the blood by controlling the secretion of parathyroid hormone (PTH). This is crucial in preventing complications such as bone disease and cardiovascular issues associated with abnormal calcium and phosphate levels. Additionally, it is also used to manage hypercalcemia in patients with parathyroid carcinoma and in cases of primary hyperparathyroidism where surgery is not an option. By modulating the calcium-sensing receptors in the parathyroid gland, cinacalcet effectively reduces PTH levels, improving patient outcomes.