The parathyroids are the endocrine glands earliest and most often affected by MEN1.
The body normally has four parathyroid glands, which are located close to the thyroid gland in the front of the neck. The parathyroids release into the bloodstream a chemical called parathyroid hormone (PTH), which helps maintain a normal supply of calcium in the blood, bones, and urine.
In MEN1, all four parathyroid glands tend to be overactive, causing hyperparathyroidism. The parathyroid glands form tumors that release too much PTH, leading to excess calcium in the blood. High blood calcium, known as hypercalcemia, can exist for many years before it is found by accident or through screening for MEN1. Unrecognized hypercalcemia can cause excess calcium to spill into the urine, leading to kidney stones or kidney damage. Also, the bones may lose calcium and weaken.
Nearly everyone who inherits a susceptibility to MEN1 will develop hyperparathyroidism by age 50, but the disorder can often be detected before age 20. Hyperparathyroidism may cause no problems for many years, or it may cause tiredness, weakness, muscle or bone pain, constipation, indigestion, kidney stones, or thinning of bones.
Doctors must decide whether hyperparathyroidism in MEN1 is severe enough to need treatment, especially in a person who has no symptoms. The usual treatment is an operation to remove most or all of the parathyroid glands. One option is to remove the three largest glands and all but a small part of the fourth. Another is to remove all four glands and at the same time transplant a small part of one gland into the forearm. By maintaining a portion of one gland, the parathyroid transplant continues to release PTH into the bloodstream to do its job.
After parathyroid surgery, regular testing of blood calcium should continue because often the small piece of remaining parathyroid tissue grows larger and causes recurrent hyperparathyroidism. If the remaining piece is in the forearm and additional surgery is needed to remove more parathyroid tissue, the arm operation can be performed under local anesthesia.
Sometimes all four glands are completely removed to prevent recurrence or may be unintentionally removed during parathyroid surgery. People whose parathyroid glands have been completely removed must take daily supplements of calcium and vitamin D or another related treatment to prevent hypocalcemia, or low blood calcium.
Source: National Endocrine and Metabolic Diseases Information Service (NEMDIS), a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK); National Institutes of Health (NIH).