What is a prolactinoma?

Prolactinomas are a benign (non-cancerous) swelling in the pituitary gland, which is situated behind the nose at the base of the brain. Prolactinoma are tumours that produce too much prolactin, a hormone which helps women to produce milk when breastfeeding and interacts with different hormones in the body.

Prolactinomas can affect men and women of all ages, but they are most common in women aged around 25 to 50. Prolactinomas affect around 1 in 10,000 people and are the most widespread form of pituitary tumour.

There are different types of Prolactinoma, which are classified according to the magnitude of the tumour and include:

  • Microprolactinomas: less than 10 mm.
  • Macroprolactinomas: more than 10 mm.
  • Giant Prolactinomas: more than 4 cm.

What causes Prolactinomas?

Prolactinomas develop as a consequence of the cells in the pituitary gland that produce prolactin multiplying more frequently than usual. It is not understood how the cells multiply or why some people develop Prolactinoma and others do not. In rare cases it is believed that there may be a genetic cause.

Symptoms of Prolactinomas

Elevated levels of prolactin in the blood can have different results on different people and symptoms tend to vary between men, women and children.

Symptoms affecting women include:

  • Irregular periods or periods stopping completely.
  • Decreased libido.
  • Reduced fertility.
  • Milk leaking from the breasts (this is normal during the end of pregnancy and during and after breastfeeding).
  • Increased growth of body and facial hair.

Symptoms affecting men:

  • Decreased libido.
  • Erectile dysfunction.
  • Reduced fertility.
  • Enlarged breasts (known as gynaecomastia).

Symptoms affecting children:

  • Delayed puberty and sexual development.
  • Delayed growth.

Complications of Prolactinomas

The main complication of a Prolactinoma is osteoporosis, which is a condition whereby the bones become thinner and weaker. Osteoporosis can usually be prevented by effectively treating the Prolactinoma; however, if further treatment is required the patient may be given testosterone or oestrogen.

If a Prolactinoma is very large it can put pressure on the brain or the nerves surrounding the brain, including the optic nerve, which can cause the following symptoms:

  • Headaches.
  • Double vision.
  • Reduced vision.

If you experience changes to your vision or headaches on a regular basis, you should see your GP.

In rare cases the tumour can press onto the pituitary gland and this can affect the production of other hormones. This can trigger other symptoms including fainting, tiredness, low blood sugar levels and also low blood pressure. In rare cases fluid that surrounds the brain can leak through the nose, in which case medical treatment should be sought immediately.

The vast majority of Prolactinomas are benign but it is possible for a tumour to be malignant (cancerous).

How are Prolactinomas diagnosed?

When you see your GP they will ask you about your symptoms. These symptoms alone may be sufficient for your doctor to surmise that you have a Prolactinoma. If so they will refer you to a specialist for further tests to confirm the diagnosis. A range of tests may be carried out, including:

  • Blood tests: a blood test will be carried out to measure the level of prolactin in the blood. If the result is higher than normal you may be advised to have another test. Levels of prolactin can fluctuate during the day, so you will be advised to have the repeat test around 2 hours after you wake up and are well rested. If the result is abnormally high (the normal level is less than 400mU/l) at more than 500mU/l, this usually indicates a Prolactinoma. Blood tests may also be carried out to check the function of the kidneys and thyroid gland.
  • Eye examination and vision tests: these are carried out to determine if the tumour is pressing on the optic nerve.
  • MRI or CT scans: these are used to measure the magnitude of the tumour.
  • Bone density scans, which may be carried out if a patient has symptoms of osteoporosis.

Treatment for a Prolactinoma

In some cases treatment may not be recommended, such as if the tumour is very small and is not causing any symptoms, whereby a policy of watchful waiting may be adopted instead. This means that your doctor will keep an eye on your condition rather than treating it immediately. Taking hormones such as oestrogen for women and testosterone for men may also help to ease symptoms.


The most widespread treatment for a Prolactinoma is medication. A type of medication known as dopamine agonists are prescribed to help reduce the amount of prolactin created by the pituitary gland and they can also reduce the magnitude of the tumour. Prolactin levels usually return to normal after a few weeks of taking dopamine agonists. The main types of dopamine agonists are known as cabergoline, bromocriptine and quinagolide. There are advantages and disadvantages to all types, which will be explained by your doctor. Possible side effects of dopamine agonists include:

  • Headaches.
  • Nausea.
  • Dizziness.
  • Feeling drowsy.

If you are planning to conceive in the near future talk to your doctor about the treatment options. Treatment can help to improve fertility and it is possible to take medication; bromocriptine is usually given to pregnant women, as it is regarded as the safest type of dopamine agonist. It is not unusual for Prolactinoma to increase in size during pregnancy and it is important that you see your doctor if you experience headaches or changes in your vision.


Surgery may be an option if medication has not been successful or the Prolactinoma is relatively large. The procedure, known as transsphenoidal surgery, involves accessing the pituitary gland through the sphenoid bone, via the upper lip or through a small opening in the wall of the nostril. The surgery is carried out under general anaesthetic and the risks will be explained before the patient agrees to have surgery.


Radiotherapy is not usually used for Prolactinoma, but may be recommended if other treatments have been unsuccessful. Radiotherapy involves focusing intensive bursts of radiation onto an affected area of the body to destroy the abnormal cells that make up the tumour.

Other treatments may be necessary if the pituitary glands have been affected in the production of other hormones.

Most Prolactinomas can be treated effectively and the outlook is positive. Patients who have had a Prolactinoma will be monitored closely, as there is a possibility of the tumour recurring.

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