Multiple endocrine neoplasia 1 (MEN1)

There are 2 types of multiple endocrine neoplasia. They are MEN1 and MEN2. Although their names are similar, they are separate conditions. This information is about MEN1.

Your body is made up of tiny building blocks called cells. Inside every cell is a set of genes. These are the instructions the cell needs to work properly. Sometimes the structure of a gene is permanently changed. The change is called a gene variant or alteration. Doctors sometimes use the term gene mutation. It means the gene no longer gives the correct instructions.

People with MEN1 have a MEN1 gene variant. The normal MEN1 gene helps stop tumours developing. The variant means that the gene cannot do its job properly. If you have the variant, you are more likely to develop certain types of tumour.

Tumours can develop at any age. About 17 in 100 people with MEN1 (17%) develop a MEN-related tumour by the age of 21. About 95 in 100 people with MEN1 (95%) develop a tumour in the parathyroid gland by the age of 50.

Genes are passed from parent to child (inherited) when a sperm and egg join to start a pregnancy (conception).

We have 2 copies of each gene – 1 from our mother and the other from our father:

• the sperm contains 1 copy of the father’s genes
• the egg contains 1 copy of the mother’s genes.

You only get 1 copy of each of your parent’s genes. If 1 parent has a gene variant, you either get the copy containing the variant or you do not. This means there is a 1 in 2 (50%) chance you inherit the variant.

A small number of people are the first in their family to have the MEN1 gene variant. This means your parents did not have it. But any children you have will have a 1 in 2 (50%) chance of inheriting it from you.

How genes are inherited

We have more information about how genes are passed on.

If you have MEN1, you will have regular tests to check for early signs of a tumour developing. This is called screening. Screening helps your doctor find and treat tumours at an early stage, usually before symptoms cause problems. Screening may start from the age of 5. You usually have it once a year. But this may depend on your situation.

Screening may involve:

• seeing a specialist doctor
• having blood tests to check hormone levels
• having scans.

You may have 1 or more scans as part of your screening. You usually have these scans at the hospital and go home on the same day.

This is the most common type of endocrine tumour that occurs with MEN1. There are 4 parathyroid glands. They are just behind the thyroid gland or sometimes inside it. This is in the front of the neck. Sometimes only 1 of the parathyroid glands is affected by a tumour. But usually there are tumours in 2 or more of the glands.

The thyroid and parathyroid glands

Parathyroid glands make parathyroid hormone (PTH). PTH helps control calcium levels in the body. Tumours in the parathyroid glands produce PTH. This leads to increased levels of PTH in the blood. This can cause your bones to release calcium from the bones into the blood. A high level of calcium in the blood is called hypercalcaemia.

High levels of calcium in the blood can make you:

• feel sick (nauseous)
• thirsty
• drowsy
• confused
• unwell
• constipated
• need to pee (pass urine) often.

If hypercalcaemia is not treated, the bones get thinner due to loss of calcium. This can lead to osteoporosis. This can cause bone pain and your bones can break more easily.

High calcium levels in the blood can also affect the kidneys. But most people are treated early, so this is not usually a problem.

You will have a blood test every year to check your calcium and PTH levels. It is important to tell your doctor if you have any symptoms that may be caused by high levels of calcium in between screening tests.

The main treatment for parathyroid tumours is surgery. Some people may have monitoring with blood tests to check calcium levels, or medicines to control the blood calcium levels.

Surgery involves removing some or all of the parathyroid glands. The surgeon may also remove the thymus gland in the upper chest. This is because there are sometimes parathyroid glands in the thymus. It also reduces the risk of a tumour developing in the thymus.

Sometimes a surgeon aims to remove 3½ parathyroid glands. They leave half a gland behind to help control calcium levels. You will need to take tablets for the rest of your life if:

• the part that is left does not work properly
• the surgeon needs to remove all the parathyroid glands.

This is to keep your calcium levels in balance.

Your surgeon will explain the different operations. This means you can decide together what is right for you.

MEN1 can cause benign tumours in the pituitary gland.

The pituitary gland is at the base of the brain, behind the top of the nose. It makes hormones that control and regulate other endocrine glands in the body. These hormones include:

• prolactin, which causes breasts to grow and produce milk
• growth hormone, which affects growth and helps to maintain healthy organs
• adrenocorticotrophic hormone (ACTH), which regulates the production of the hormone cortisol by the adrenal glands.

The brain

Pituitary tumours can cause symptoms by pressing on the optic nerve. This is the nerve between the eye and the brain. Pituitary tumours can cause headaches and changes in eyesight. Other symptoms can be caused by a change in normal hormone levels.

You usually have a blood test every year and a CT or MRI scan of the pituitary gland every 3 years to check for any growths.

These are the most common type of pituitary tumour in people with MEN1. Prolactinomas can cause:

• a milky discharge from the breasts
• monthly periods to stop
• problems with erections (erectile dysfunction)
• infertility.

Tumours that make too much growth hormone can cause abnormal growth. Hands, feet, the lower jaw and brows can get larger. This is called acromegaly. These tumours may also cause high blood pressure, diabetes or excess sweating.

High levels of ACTH can lead to a condition called Cushing’s syndrome. Symptoms include weight gain, a rounder face shape, and low mood (depression). It can also cause increased facial hair growth.

You may be given tablets or injections that reduce the amount of the hormone the tumour is producing.

If your symptoms are not controlled by drugs, your doctor may talk to you about having an operation to remove the pituitary tumour. A surgeon usually does this through a small cut inside the nose. Most people fully recover from the operation within 2 weeks.

Some people may need radiotherapy after surgery to destroy any remaining tumour cells. Radiotherapy uses high-energy rays to destroy cells.

We have more information about treating pituitary tumours.

If you have MEN1, there is a 1 in 2 (50%) chance your child could inherit it from you. If you are planning to get pregnant or start a pregnancy, talk to your genetics specialist about your options.

Sometimes tests and fertility treatments can be used to ensure a parent’s gene variant is not passed to a child. The Human Fertilisation Embryology Authority (HFEA) and Genetic Alliance UK have information about this.

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