The parathyroid glands help regulate calcium absorption, use, and removal by the body. They do this by producing parathyroid hormone (PTH). PTH helps regulate calcium, phosphorus, and vitamin D levels in the blood and bone. It is important for healthy bones.

Parathyroid hyperplasia may occur in people without a family history of the disease, or as part of 3 inherited syndromes:

• Multiple endocrine neoplasia I (MEN I)
• MEN IIA
• Isolated familial hyperparathyroidism

In people with an inherited syndrome, a changed (variant) gene is passed down through the family. You only need to get the gene from one parent to develop the condition.

• In MEN I, problems in the parathyroid glands occur, as well as tumors in the pituitary gland and pancreas.
• In MEN IIA, overactivity of the parathyroid glands occurs, along with tumors in the adrenal or thyroid gland.

Parathyroid hyperplasia that isn't part of an inherited syndrome is much more common. It occurs due to other medical conditions. The most common conditions that can cause parathyroid hyperplasia are chronic kidney disease and chronic vitamin D deficiency. In both cases, the parathyroid glands become enlarged because vitamin D and calcium levels are too low.

Symptoms may include:

• Bone fractures or bone pain
• Constipation
• Lack of energy
• Muscle pain
• Nausea

Blood tests will be done to check levels of:

• Calcium
• Phosphorus
• Magnesium
• PTH
• Vitamin D
• Creatinine, BUN (kidney function tests)
• 24-hour urine test - done to determine how much calcium is being filtered out of the body into the urine
  
• Alkaline phosphatase
  

Other tests include:

• Bone density exam
• Kidney ultrasound or CT scan (may show kidney stones or calcification)
• Kidney x-rays (may show kidney stones)
• MRI
• Neck ultrasound
• Sestamibi neck scan (to identify the location of the parathyroid adenoma)

If parathyroid hyperplasia is due to kidney disease or low vitamin D level and it is found early, your health care provider may recommend that you take vitamin D, vitamin D-like medicines, and other medicines.

Surgery is usually done when the parathyroid glands are producing too much PTH and causing symptoms. Usually 3 1/2 glands are removed. The remaining tissue may be implanted in the forearm or neck muscle. This allows easy access to the tissue if symptoms come back. This tissue is implanted to prevent the body from having too little PTH, which can result in low calcium levels (from hypoparathyroidism).

After surgery, a high blood calcium level may persist or return. Surgery can sometimes cause hypoparathyroidism, which makes blood calcium level too low.

Parathyroid hyperplasia can cause hyperparathyroidism, which leads to an increase in blood calcium level.

Complications include increased calcium in the kidneys, which can cause kidney stones, and osteitis fibrosa cystica (a softened, weak area in the bones).

Surgery can sometimes damage the nerves that control the vocal cords. This can affect the strength of your voice.

Complications may result from the other tumors that are part of the MEN syndromes.

Contact your provider if:

• You have any symptoms of hypercalcemia
• You have a family history of a MEN syndrome

If you have a family history of the MEN syndromes, you may want to have genetic screening to check for the variant gene. Those who have the variant gene may have routine screening tests to detect any early symptoms.

Enlarged parathyroid glands; Osteoporosis - parathyroid hyperplasia; Bone thinning - parathyroid hyperplasia; Osteopenia - parathyroid hyperplasia; High calcium level - parathyroid hyperplasia; Chronic kidney disease - parathyroid hyperplasia; Kidney failure - parathyroid hyperplasia; Overactive parathyroid - parathyroid hyperplasia

Reid LM, Kamani D, Randolph GW. Management of parathyroid disorders. In: Flint PW, Francis HW, Haughey BH, et al, eds. Cummings Otolaryngology: Head and Neck Surgery. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 123.

Thakker RV. The parathyroid glands, hypercalcemia and hypocalcemia. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 227.

Walker MD, Bilezikian JP. Primary hyperparathyroidism. In: Robertson RP, ed. DeGroot's Endocrinology. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 54.

Updated by: Sandeep K. Dhaliwal, MD, board-certified in Diabetes, Endocrinology, and Metabolism, Springfield, VA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.