tertiary hyperparathyroidism

Tertiary hyperparathyroidism represents the final stage in the progression of parathyroid gland dysfunction, typically developing after prolonged secondary hyperparathyroidism. The pathophysiology involves chronic stimulation of parathyroid glands (usually due to hypocalcemia, hyperphosphatemia, and low calcitriol in CKD) leading to parathyroid hyperplasia and eventually autonomous function. Unlike secondary hyperparathyroidism where PTH elevation is appropriate compensation, tertiary involves inappropriate PTH secretion that continues despite normalization of calcium, phosphorus, and vitamin D levels. This results in hypercalcemia, hypercalciuria, nephrolithiasis, bone disease, and potential cardiovascular complications. The condition is most commonly encountered in post-kidney transplant patients where 15-50% develop persistent hyperparathyroidism. Other causes include prolonged vitamin D deficiency or malabsorption syndromes. Diagnosis involves elevated or inappropriately normal PTH levels in the setting of hypercalcemia. Treatment includes calcimimetics (cinacalcet), vitamin D receptor activators, and in severe cases, parathyroidectomy. The condition highlights the importance of early management of secondary hyperparathyroidism to prevent autonomous parathyroid function.