Secondary hyperparathyroidism is a condition in which a disease outside of the parathyroid glands causes all of the parathyroid glands to become enlarged and hyperactive. The most common causes of secondary hyperparathyroidism are kidney failure and vitamin D deficiency. In kidney failure, the kidney is no longer able to make enough vitamin D or remove all of the phosphorus that is made by the body, which leads to low calcium levels. These low calcium levels stimulate the parathyroid glands to make more PTH. Over time, this constant stimulation causes the parathyroid glands to grow and become hyperactive and patients can progress to develop secondary hyperparathyroidism. Patients with kidney failure and secondary hyperparathyroidism can often have PTH levels in the hundreds and even thousands. Occasionally patients will develop a condition called calciphylaxis where calcium deposits form in the skin and muscles causing painful skin lesions that over time can cause necrosis (i.e. tissue death) and ulcers.
The best treatment for secondary hyperparathyroidism is typically aimed at fixing the cause of the parathyroid problem. For example, patients with secondary hyperparathyroidism from vitamin D deficiency are best treated by raising the vitamin D levels to the normal range. For patients with secondary hyperparathyroidism from kidney failure, the only treatment is to have a kidney transplant. If the underlying problem cannot be fixed, the best treatment is medical therapy and surgery is only done for patients in whom optimal medical therapy is not working. For patients with kidney failure, the main treatments include phosphate binders (to bind the extra phosphate), vitamin D supplements (i.e. calcitriol), and calcimimetics. Calcimimetics are drugs that "trick" parathyroid cells into making less PTH. Calcimimetics like Sensipar lower the PTH levels by about 50% on average. The main side effects of calcimimetics include nausea and vomiting.
Unfortunately, medical therapy does not work in up to 25% of patients and surgery is sometimes necessary. The main reasons for an operation include: worsening bone density, severe pruritus (i.e. uncontrollable itching), calciphylaxis, PTH levels that are consistently higher than 800 pg/ml, and inability to control calcium and phosphorus levels in the blood by dialysis. The three main types of surgery for secondary hyperparathyroidism are subtotal parathyroidectomy (i.e. removal of 3 and ½ of the parathyroids), 4 gland excision and autotransplantation (i.e. removing all 4 parathyroid glands and placing a piece of a parathyroid in the forearm), and PTH-guided parathyroidectomy (i.e. removing enough parathyroid tissue to bring the intraoperative PTH levels to between 200 and 300). Each technique has its risks and benefits, so it is important to work with specialists to determine which operation is right for each individual patient. However, since none of these operations fix the underlying cause of the secondary hyperparathyroidism, patients are at high risk for recurrence (i.e. disease that comes back).