Parathyroid tumours and disease

Parathyroid tumours are common tumours of the endocrine system. Most parathyroid tumours are non-cancerous (benign) growths that do not spread to other parts of the body. In rare cases, parathyroid tumours are cancerous (malignant), which means they can grow into and destroy nearby tissue. They can also spread (metastasize) to other parts of the body.

Most people with parathyroid tumours have hyperparathyroidism (overactive parathyroid glands). This is a common disease when one or more of the parathyroid glands make too much parathyroid hormone (PTH). Hyperparathyroidism causes too much calcium in the blood (called hypercalcemia). This can cause serious health problems if it’s not treated. It is also called primary hyperparathyroidism.

Parathyroid adenomas are non-cancerous parathyroid tumours. They are the most common type of tumour that can develop in the parathyroid glands. A parathyroid adenoma usually forms in only one parathyroid gland. Less often, parathyroid adenomas can be found in 2 or 3 of the parathyroid glands.

Parathyroid adenomas are the most common cause of hyperparathyroidism. The tumours are mainly made up of chief cells, which are the main cells of the parathyroid glands that make and release PTH. Parathyroid adenomas cause parathyroid glands to enlarge and become overactive. About 80% to 90% of people with primary hyperparathyroidism have a parathyroid adenoma in one parathyroid gland.

The main treatment for parathyroid adenoma is surgery to completely remove the parathyroid gland (called a parathyroidectomy).

Parathyroid hyperplasia is a non-cancerous condition where all 4 parathyroid glands are enlarged. It causes hyperparathyroidism. About 5% to 15% of people with primary hyperparathyroidism have parathyroid hyperplasia.

Parathyroid hyperplasia usually happens by chance (is sporadic). Sometimes it can be caused by a hereditary condition, including multiple endocrine neoplasia (MEN).

The treatment for parathyroid hyperplasia is surgery to remove 3-1/2 of the 4 parathyroid glands.

Parathyroid cancer is a cancerous tumour of the parathyroid gland. It is also called parathyroid carcinoma. Parathyroid cancer is very rare. Less than 1% of people with primary hyperparathyroidism have parathyroid cancer.

But most people with parathyroid cancer have hyperparathyroidism and symptoms of hypercalcemia.

Parathyroid cancer usually grows slowly (is indolent). It tends to grow into or attach to nearby areas such as the thyroid and soft tissue. Parathyroid cancer tends to be larger than a parathyroid adenoma.

It is often hard to tell the difference between parathyroid cancer and a parathyroid adenoma based on imaging and other tests. They have similar signs and symptoms. Doctors usually need to do surgery to make a diagnosis of parathyroid cancer.

The following non-cancerous conditions can also affect the parathyroid glands:

• secondary hyperparathyroidism (overactive parathyroid glands caused by conditions outside the parathyroid glands, such as kidney disease)
• hypoparathyroidism (low levels of PTH)
• parathyromatosis (pieces of parathyroid tissue scattered throughout the tissues of the neck and middle of the chest)