Prolactinoma: what to know

A prolactinoma is a type of brain tumour that is not cancerous, but does still affect the brain by causing the pituitary gland to overproduce a hormone called prolactin. In this article, consultant neurosurgeon Professor Marcus Hani shares an overview of prolactinomas.

The following information is based on the Diagnosis and management of prolactin-secreting pituitary adenomas: a Pituitary Society international Consensus Statement, which was co-authored by Professor Marcus and published in Nature Reviews Endocrinology in 2023.

What is a prolactinoma?

A prolactinoma is a benign (non-cancerous) tumour of the pituitary gland that produces too much of the hormone prolactin.

Prolactin helps control fertility and breast milk production. When levels are too high, it can affect hormone balance and reproductive health.

Prolactinomas are the most common type of hormone-producing pituitary tumour.

What symptoms can it cause?

Symptoms can develop slowly and may be present for some time before diagnosis.

They are usually due to either raised prolactin levels or the size of the tumour.

In women

• irregular or absent periods
• milky nipple discharge
• reduced sex drive
• difficulty becoming pregnant

In men

• reduced sex drive
• erectile dysfunction
• infertility
• breast enlargement
• If the tumour is large
• headaches
• vision problems
• tiredness due to hormone deficiency

How is a prolactinoma diagnosed?

Assessment usually includes:

• blood tests confirming raised prolactin
• tests to rule out other causes (such as medications or thyroid problems)
• an MRI scan of the pituitary gland
• vision testing if the tumour is large

Not all raised prolactin levels are due to a prolactinoma, so careful assessment is important.

How is a prolactinoma treated?

There are two main treatment options:

• medication (the most common first treatment)
• surgery (in selected situations)

For many people, both options may be reasonable, particularly for small tumours. The best approach is individualised.

Treatment with medication

Most prolactinomas are treated with medicines called dopamine agonists (most commonly cabergoline).

These medicines can:

• lower prolactin levels
• shrink the tumour
• restore fertility and hormone balance

For many patients, medication works very well and avoids the need for an operation.

However, treatment is often long term, and some people experience side effects such as nausea, dizziness, or mood changes.

When might surgery be considered?

Surgery may be offered as an alternative to medication in carefully selected patients, particularly if the tumour is small (a microprolactinoma).

This may be appropriate if:

• the tumour is small and well-defined
• the patient prefers a potential one-off treatment rather than long-term medication
• medication causes side effects or is not desired
• care is provided in a specialist pituitary centre

In experienced centres, surgery can offer a good chance of long-term cure for small tumours.

When is surgery recommended?

In some situations, surgery is more clearly advised. For example:

• if medication is not tolerated
• if medication does not work well enough
• if the tumour is affecting vision
• if more rapid treatment is needed

Radiotherapy is usually reserved for rare, difficult, or aggressive tumours.

How do patients choose between treatments?

Choosing between medication and surgery is a shared decision between the patient and their specialist team.

The decision is usually based on three main areas:

The tumour

• prolactin level and tumour behaviour
• size and appearance on MRI
• whether it is close to the optic nerves
• likelihood of cure with surgery

The centre

• experience of the pituitary surgical team
• expected success and complication rates

The patient

• tolerance of medication and whether it works well enough 
• preference for long-term treatment versus a one-off procedure
• plans for pregnancy
• personal priorities

There is no single right answer. The best approach is tailored to each individual.

What is the long-term outlook?

The outlook for prolactinoma is generally excellent.

Most patients:

• respond well to treatment
• regain normal hormone function
• lead normal lives with regular monitoring