Prolactin

Prolactin levels are used with other tests, to help:

• Determine the cause of galactorrhoea
• Determine the cause of headaches and visual disturbances
• Diagnose infertility and erectile dysfunction in males
• Diagnose infertility in females
• Diagnose prolactinomas (tumours of the pituitary gland that produce prolactin)
• Evaluate pituitary gland function (along with other hormones)
• Monitor treatment of prolactinomas and detect recurrences

Prolactin levels may be used when a patient has symptoms of a prolactinoma such as unexplained headaches, visual impairment, and/or galactorrhoea. They may also be used, along with other tests, when a woman is experiencing infertility or irregular periods; or when a man has symptoms such as: a decreased sex drive, galactorrhoea, or infertility. Prolactin levels are also often ordered in men as a follow-up to a low testosterone level.

When a patient has a prolactinoma, prolactin levels may be used to monitor the growth of the tumour and its response to treatment. They may also be used at regular intervals to monitor for prolactinoma recurrence.

Prolactin levels may be used with other hormone levels such as growth hormone, when your doctor suspects that you have more general hypopituitarism (low levels of pituitary function which result in lowered levels of hormones being produced). Prolactin levels may also be monitored when you have a condition or are taking medications that affect dopamine (a brain chemical that controls the production of prolactin).

Men and non-pregnant women will normally have only small amounts of prolactin in their blood. The levels are ideally interpreted knowing when the sample was collected. The levels will vary over a 24 hour period - rising during sleep and peaking in the morning. Ideally, your blood sample should usually be taken a couple of hours after waking up, preferably after you have been resting quietly for 30 minutes (although your doctor may have his or her own reasons for doing them at other times).

High levels of prolactin (hyperprolactinaemia) are normal during pregnancy, and after childbirth while the mother is breastfeeding. High levels can also be seen with:

• Anorexia nervosa
• Drugs: Oestrogen, tricyclic antidepressants, and drugs that block the effect of dopamine (a brain chemical that controls the production of prolactin) such as tranquilizers, some hypertension drugs, and some drugs that are used to treat gastro-oesophageal reflux
• Hypothalamic diseases
• Hypothyroidism
• Kidney disease
• Nipple stimulation (small increase)
• Other pituitary tumours and diseases
• Polycystic ovary syndrome (PCOS)
• Prolactinomas
• Macroprolactinaemia

Levels of prolactin that are below normal are not usually treated but may be indicative of a more general hypopituitarism (decreased pituitary function and decreased hormone production). Low levels may also be caused by drugs such as dopamine, levodopa, and ergot alkaloid derivatives.

Stress from illness, trauma, work and personal problems, and even the fear of having the blood test done can cause moderate increases in prolactin.

Prolactinomas are often small. Your doctor may request an MRI (magnetic resonance imaging) scan to help locate the tumour within the pituitary gland and to look at both the size of the tumour and the size of the pituitary (which often enlarges).