Multiple Endocrine Neoplasia (MEN) Type 1 Defined
As discussed in Understanding Multiple Endocrine Neoplasia, MEN is a group of hereditary disorders that causes tumors to grow in the body’s endocrine organs, the glands that produce hormones. MEN is separated into two distinct types: Type 1 and Type 2. This article focuses on MEN Type 1.
The symptoms of patients with MEN type 1 depend upon the location, size, and activity of their endocrine tumors.
Impact on the Pituitary Gland
The pituitary gland is normally about the size of a pea and it sits at the base of the brain, just above the innermost sinuses. It is a master gland that is responsible for the production of a variety of hormones that control, or contribute to: growth, sexual development, blood pressure, regulation of the thyroid gland, water intake, and, in women, production of breast milk and contractions in the uterus. Because the gland is so small and confined to a tiny space in the skull, when a tumor grows in the pituitary, it does not have much room to expand and it starts to press on the optic nerve directly above it. Pushing on this nerve can cause problems with vision, typically a partial blindness in which the outer half of each eye’s vision is lost.
A pituitary tumor (also called an adenoma) can still cause problems by overproducing one or more of the hormones that the gland normally releases. How the patient experiences this hormonal excess depends upon which hormone (or hormones) are being made in abundance. For instance, overproduction of the hormone called prolactin can result in the release of breast milk, even in a woman who is not breastfeeding or in a man who would presumably never be breastfeeding at all!
Impact on the Parathyroid Gland
The parathyroid glands are located at the base of the neck, not far above the space between the collarbones. There are 4 glands, each about the size of a grain of rice, that sit behind the thyroid gland (hence their name, which means “near thyroid”). They are responsible for controlling the level of calcium in the body.
In MEN type 1, most patients develop hyperparathyroidism (meaning overactive parathyroid glands) and high calcium levels. High calcium levels can be experienced by the patient in a variety of ways: bone pain, kidney stones, abdominal pain & constipation, and depression/sluggishness. No one of these symptoms is only caused by high calcium levels (there are a number of other medical problems that can cause each one) but when they are seen together in the same patient, they are more likely to be recognized as the result of high calcium. Because it is important to put all these problems together, this cluster of symptoms is sometimes remembered by doctors through the phrase “bones, stones, groans, and moans.”
Impact on the Pancreas Gland
The pancreas is a part of the digestive system that helps to process food (although food does not pass directly through it) and it also releases hormones that travel throughout the body (most famously, when the pancreas does not make insulin, patients develop diabetes). It sits at the back of the abdomen, just below the stomach and behind the small intestine, and is normally not bothersome to patients unless it grows abnormally large or stops doing one of its many important jobs.
MEN type 1 patients often develop tumors in their pancreas without knowing it. These tumors are NOT the same kind of cancer that is normally implied when people use the term “pancreatic cancer”. That is a different and much more worrisome type of cancer in the pancreas which is more precisely known as pancreatic adenocarcinoma. Instead, patients with MEN type 1 tend to develop tumors in the pancreas called islet cell tumors. Just like with the pituitary adenomas overproducing pituitary hormones, these tumors may become symptomatic because they make too much of one of the pancreatic hormones, including insulin. They are sometimes named by the hormone that they overproduce, meaning that an islet cell tumor making lots of insulin is called an insulinoma, and an islet cell tumor making the hormone gastrin is called a gastrinoma.