MEN1 is typically characterised by tumours in the following locations of the body:
1. Parathyroid glandsAbout 95% of people with MEN1 develop tumours in the parathyroid glands by age 50.These four pea-sized glands produce the parathyroid hormone, which helps to maintain the right balance of calcium and phosphate in your body. Over time, MEN1 can affect all four glands.MEN1-related tumours cause the parathyroid glands to become overactive, producing too much parathyroid hormone. This condition, called hyperparathyroidism, is the most common complication associated with MEN1.
The parathyroid glands are located near the thyroid gland in the neck
Excess parathyroid hormone can cause calcium levels in your blood to rise too high. Complications may include:
2. Pancreas and digestive tractAbout 40% of people with MEN1 develop tumours in the pancreas, duodenum (small intestine), or other parts of the digestive tract.Many different types of tumours may develop at the same time. Many of these tumours produce hormones while others do not. Some tumours may be cancerous.In people with MEN1, the two most common tumours of the digestive tract are:
Other rare pancreatic tumours include:
3. Pituitary glandNearly one in three people with MEN1 develop tumours in the front part of the pituitary gland called the anterior lobe. Like other pituitary tumours, these growths are often small in size and are almost always noncancerous.
The pituitary gland sits at the base of the brain
In people with MEN1, the two most common pituitary tumours are:
Prolactinomas. These tumours are the most common, and produce the hormone prolactin. Normally, this hormone signals women’s breasts to produce milk during pregnancy and breastfeeding. Women with a prolactinoma may notice milk discharge from their breast(s) (galactorrhea) when they are not pregnant or breastfeeding. In both men and women, high prolactin levels can lead to infertility and bone loss.
Growth hormone (GH) tumours. These tumours are the second most common, and produce excess GH which causes bones and other vital organs to grow larger in size. This condition is called acromegaly. Health problems caused by excessive GH include hypertension, diabetes, heart disease, stroke, arthritis, carpal tunnel syndrome and tumours of the colon or rectum.Pituitary tumours that grow large in size may prevent the pituitary gland from making enough hormones, leading to a condition called hypopituitarism.The tumours may also press against nearby brain tissues such as the eye nerve, causing vision problems and headaches.Hypopituitarism can usually be treated with oral hormone replacement pills.
Other tumoursMEN1 can also cause tumours to develop in other parts of the body. Examples include:
Note: The conditions associated with MEN1 and their risk estimates may change as more information is available.
While individuals with MEN1 have an increased risk of the tumours listed above, it does not mean that they will definitely develop tumours associated with MEN1.
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