The multiple endocrine neoplasias, or MEN for short, are a group of inherited diseases which cause tumors to grow in the endocrine glands of the body.
The endocrine glands affected in multiple endocrine neoplasia are the pituitary gland, the thyroid gland, the parathyroid glands, the adrenal glands and the pancreas.
So in multiple endocrine neoplasias there are tumors that form in these glands that lead to overproduction of hormones.
Let’s start by going through the glands that are affected and what they do.
The pituitary gland is a pea-sized gland found at the base of the brain that makes hormones to control many of the other endocrine glands in the body.
These hormones include thyroid stimulating hormone which acts on the thyroid to make thyroid hormone, adrenal corticotropic hormone that acts on the adrenal glands to make cortisol, follicle stimulating hormone and luteinizing hormone which acts on the ovaries and testes to make estrogen in women and testosterone in men.
So it’s like the king of the endocrine glands telling them how much hormone to produce.
The pituitary also makes growth hormone which makes you grow, prolactin which stimulates milk production in women, oxytocin which triggers milk release, antidiuretic hormone which help the kidneys reabsorb water, and melanocyte stimulating hormone helps the melanocytes create more melanin or pigment.
Next, in the neck is the thyroid gland which makes thyroid hormones that control the metabolic rate, as well as calcitonin, a hormone that decreases calcium levels.
Within the thyroid gland, are buried four parathyroid glands which make parathyroid hormone which increases calcium levels.
Lower down, there are the adrenal glands which sit just above each kidney and produce epinephrine and norepinephrine which are fight or flight hormones that increase cardiac output, dilate the pupils, and increase blood flow to the muscles.
Finally, there’s the pancreas which makes insulin to help lower blood sugar, and glucagon to help raise blood sugar.
The pancreas also makes gastrin which increases hydrochloric acid production in the stomach, and vasoactive intestinal peptide which relaxes the intestinal wall allowing food to pass.
Multiple endocrine neoplasias are caused by genetic mutations to one of two genes, either MEN1 or RET.
Both of these genes have a dominant inheritance pattern, so you only need one copy of the mutated gene to get the disease.
The MEN1 gene is found on chromosome 11 and is a tumor suppressor gene, meaning it normally stops a cell from dividing uncontrollably.
An MEN1 mutation causes MEN type 1.
On the other hand, RET is a proto oncogene which promotes normal cell division, and when it mutates, it becomes an oncogene which promotes constant cell division.
Mutated RET causes multiple endocrine neoplasia type 2A and 2B.
In multiple endocrine neoplasia type 1, there are three types of tumors: parathyroid, pancreatic, and pituitary.
The most common tumor is a parathyroid tumor.
Increased parathyroid hormone causes increased bone breakdown which leads to hypercalcemia and calcium kidney stones.
Pancreatic tumors cause problems based on the type of hormone they produce.