How is a prolactinoma diagnosed?

The tests to diagnose a prolactinoma are relatively straightforward. They consist of blood tests to check hormone levels and a scan of the pituitary gland to show the size of the prolactinoma.

Blood Tests

Your GP may carry out initial tests on your prolactin and thyroid levels. You then would need to attend a specialist endocrine clinic as an outpatient for further tests, including any scans.

Stress and the insertion of a needle to take a blood sample can slightly raise your prolactin level, so it should be repeated more than once to ensure the result is consistently high and a true value.

A further blood sample will be taken to make sure your thyroid gland is functioning normally. The other hormones produced by the pituitary will also need to be checked; this can be done by a single blood sample.

Some specialists may recommend further tests to better assess pituitary gland function. These will be explained to you should you fall into this category. Mostly, these investigations involve timed blood sampling and possible administration of a hormone or specific drug to produce stimulation or suppression.


A scan is usually carried out to give detailed pictures of the pituitary gland. There are two types of scan:

  • MRI (magnetic resonance imaging, using a special magnetic technique)
  • CT or CAT (computerised tomography, using X-ray imaging)

MRI is the scan of choice. Both types of scan involve you lying on a moveable table and passing into a cylindrical piece of equipment. You may find the examination a bit noisy or claustrophobic, but you will probably find that it does not give you too much trouble. If you feel it might cause you concern, ask your GP beforehand if you can have a sedative to take. During the scan, the radiologist may inject a special dye into your arm so that your prolactinoma can be seen more clearly.

A minority of patients are allergic to this injection, so do tell the specialist if you have asthma or any allergies.

Other Tests

If you have any problems with your vision, you will probably be seen by an eye specialist (opthalmologist) who will check the strength of your eyesight and chart your fields of vision.

Sometimes an X-ray scan of your spine and hip bones (bone densitrometry) may be recommended to see whether there is any evidence of thinning of the bones (osteoporosis). This is a painless and straightforward test commonly called a DEXA scan.

Women who have not had periods for a year, and male patients with prolonged low testosterone levels should be offered bone density tests to ensure that they are not developing osteoporosis.