Prolactin is a hormone, which is produced by the anterior pituitary gland; its principal role is to stimulate lactation (the production of breast milk). Prolactin is present in males and females but only in very small amounts; the level increases significantly throughout pregnancy. The amount of prolactin in the body is controlled by a chemical known as dopamine.

Levels of prolactin increase during pregnancy and start to fall after the mother has given birth; if the mother is breastfeeding, prolactin will stimulate milk production. If a mother stops breastfeeding, the levels of prolactin will start to decrease and this will slow milk production.

Why is the test used?

The test is used to measure the amount of prolactin in the body; this information can be useful in the investigation and diagnosis of a range of conditions, including:

  • Prolactinoma (tumours in the pituitary gland, which produce prolactin)
  • Galactorrhoea (the production of breast milk or discharge in a non-pregnant person)
  • Infertility (in both males and females)
  • Erectile dysfunction in males

The test may also be used to assess pituitary gland function.

The test is usually ordered when a patient has symptoms of prolactinoma, including unexplained headaches, galactorrhoea and problems with their vision.

The test may also be ordered when a couple are having trouble conceiving or a man is suffering from erectile dysfunction.

If a patient is diagnosed with prolactinoma, the test may be repeated to monitor their condition and assess the efficacy of the treatment.

How is the test done?

The test is performed by taking a sample of blood from a vein in the arm (usually on the inside of the elbow). A needle is inserted into the vein and the blood is drawn out and collected using a syringe. Once a sufficient sample has been taken, the blood will be bottled, labelled with the patient’s name and sent away to the laboratory for analysis.

What do the test results mean?

High levels of prolactin are normal during pregnancy and after childbirth; if levels are high in a male or a non-pregnant female, this may indicate that the patient has health conditions, which may be causing them to produce too much prolactin; these include:

  • Prolactinoma
  • Hypothyroidism (underactive thyroid gland)
  • Kidney disease
  • Anorexia nervosa
  • Hypothalamic conditions (affecting the hypothalamus)
  • PCOS (polycystic ovarian syndrome)

Taking medication, including oestrogen and some forms of anti-depressant may also cause the level of prolactin to increase.

Low levels of prolactin are not usually a cause for concern but they may indicate a general problem with the functioning of the pituitary gland so further tests may be carried out.

Stress may affect levels of prolactin.

Specific Blood Tests

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