Pituitary Adenoma Explained

A pituitary adenoma is a growth that develops in the pituitary gland, a small gland at the base of the brain that helps direct much of the body's hormone system. Most are non-cancerous. Some make excess hormones, while others cause problems by their size. They are evaluated with hormone tests and imaging and are generally managed according to type and symptoms.

What a pituitary adenoma is

The pituitary gland is often called the "master gland" because it releases hormones that direct other glands, including the thyroid, adrenal glands, and reproductive organs, as well as hormones involved in growth, milk production, and water balance. A pituitary adenoma is a growth arising from the gland's own cells. The great majority are benign (non-cancerous) and grow slowly. For background on the wider hormone system, see our hormones section.

Adenomas are often described in two ways. By behaviour, they may be "functioning" (making excess of a particular hormone) or "non-functioning" (not making excess hormone but potentially causing effects through their size). By size, smaller and larger growths are sometimes distinguished. A functioning adenoma that makes prolactin is related to the topic of high prolactin, while others can affect growth hormone or the body's cortisol pathway. The variety is why each case is assessed individually.

Common signs and symptoms

Symptoms depend on whether the adenoma makes excess hormone, which hormone is involved, and whether its size affects nearby structures. Reported features may include:

• Hormone-excess effects, which vary by hormone — for example changes in periods or milk production with excess prolactin, or features linked to excess growth hormone or cortisol
• Headaches
• Vision changes, especially loss of side vision, if the growth presses on nearby nerves
• Signs of reduced output of other pituitary hormones, such as tiredness or changes in sexual function
• Sometimes no symptoms, with the growth found incidentally on a scan done for another reason

Because the pituitary influences so many systems, the picture varies widely from person to person.

What causes it

In most cases the reason a pituitary adenoma develops is not known, and it is generally not something a person could have prevented. Most occur on their own without a clear inherited cause. Occasionally they are linked to rare inherited conditions that predispose to tumours in hormone-producing glands, and a clinician may consider family history where relevant. Pituitary adenomas are common findings overall, and many small ones never cause problems.

How it is diagnosed

Diagnosis combines hormone tests, which show whether the gland is making too much or too little of various hormones, with imaging that shows the gland itself. A clinician interprets these together. Common evaluations include:

• Hormone blood tests — measuring pituitary hormones and the hormones of the glands they control, to detect excess or deficiency. See the prolactin levels guide.
• Imaging — detailed pictures of the pituitary, which can show the size and position of a growth.
• Vision testing — checking side vision when a growth may be affecting nearby nerves.
• Dynamic testing — tests that observe how hormones respond to a stimulus, used in selected cases.

The table below gives illustrative reference points only; actual ranges vary by laboratory, age, and sex, so results should be interpreted with a clinician.

These entries are illustrative and not diagnostic cut-offs. For background on the markers, see our blood tests section.

How it is generally managed

Management depends heavily on the type of adenoma, its size, whether it makes excess hormone, and the symptoms it causes. The plan is individual and decided with a specialist team, and general approaches can include:

• Observation — small, non-functioning growths that cause no problems may simply be monitored over time.
• Medicines — for some functioning adenomas, medicines may address the hormone excess; choices are individual and decided with a clinician.
• Surgery — considered for some growths, particularly when size affects nearby structures.
• Other treatments — additional approaches such as targeted radiation are used in selected situations.
• Hormone support — if the gland's normal output is reduced, replacing affected hormones may be needed, as advised.

General treatment principles are outlined in our treatments section. Note that excess prolactin from an adenoma is a common scenario covered under high prolactin, and reduced overall pituitary output is its own topic. This page is educational and is not a substitute for personalised medical advice, and it does not describe doses or specific regimens.

Established understanding versus ongoing research

The core picture — that most pituitary adenomas are benign, that they can act by making excess hormone or by their size, and that management depends on type — is well established. Other areas, including why most arise and how best to manage particular subtypes, remain active topics of study. Where evidence is still developing, decisions are best made with a specialist team.