Prolactin
Prolactin is the hormone that triggers breast-milk production, made by a small gland at the base of the brain. A raised level is common and most often comes from certain medicines or a small, usually harmless growth on that gland — and it can even rise just from the stress of the blood test itself. A mildly raised result is usually rechecked before reading much into it.
Targeted TestingWhat is prolactin?
Prolactin is a hormone produced by the lactotroph cells of the pituitary gland — a grape-sized organ at the base of the brain that controls many other hormones. Its primary job is to trigger and maintain breast milk production. Outside of breastfeeding, prolactin also plays a role in reproductive function and the regulation of the menstrual cycle. The most common causes of a raised prolactin level are certain prescribed medicines and prolactinomas — prolactin-producing tumours of the pituitary gland. Prolactinomas are almost always benign (non-cancerous).
Why is it tested?
A prolactin test is ordered when you have symptoms that might relate to elevated prolactin — technically called hyperprolactinaemia (too much prolactin in the blood). These symptoms can include milk production when you are not breastfeeding (a condition known as galactorrhoea — spontaneous milk release unrelated to pregnancy or breastfeeding), irregular or absent periods, unexplained fertility difficulties, or low sex drive. It may also be tested if there are other signs suggesting a pituitary gland problem, such as persistent headaches or changes in vision. Hyperprolactinaemia is a relatively common endocrine (hormonal) abnormality, and most causes are explainable and manageable once identified.
Reference range (Australia)
Reference intervals for prolactin are method-dependent — different laboratory analysers produce different cut-points. A mildly raised result is typically rechecked because stress and the blood draw itself can transiently raise prolactin. Pregnancy and breastfeeding raise prolactin substantially above non-pregnant reference intervals. Always use the interval printed on your own report.
Reference intervals vary between laboratories. Always use the range printed on your own report.
What your result means
A low prolactin level is generally not clinically significant in people who are not breastfeeding. It does not usually require follow-up on its own.
A result within the reference interval for your laboratory suggests prolactin is in the expected range. Because prolactin is assay-dependent — the specific measuring method affects the result — the interval on your own report is the relevant guide.
A prolactin result above the reference interval — hyperprolactinaemia — has several possible causes, most of which are not alarming. Certain medicines are among the most common: drugs that work on the brain's dopamine pathways, such as antipsychotics (for example risperidone), can raise prolactin as a direct effect. Prolactinomas — benign pituitary tumours that produce prolactin — are the most common pathological cause, and even these are almost always non-cancerous; if one is found, your GP can explain the options for managing it. A mildly raised result can also result from the blood draw itself — the stress and discomfort of venepuncture (taking blood from a vein) can transiently push prolactin up. For this reason, a mildly elevated result is often repeated under calmer conditions before any conclusions are drawn. Your GP will consider medicines you take, the degree of elevation, and your symptoms when working out what is most likely driving it.
What can affect your result
Several factors can raise prolactin, and understanding them is helpful when reading a result. Medicines are a major cause: drugs that impair the release of dopamine (a brain chemical that normally suppresses prolactin) lead to increased prolactin secretion. Antipsychotics such as risperidone are a well-known example, but many other medicines can have this effect. The blood draw itself can temporarily raise prolactin — the physical stress of venepuncture (taking blood) means results should ideally be collected with minimal distress, and a mildly elevated result may prompt a repeat test under calmer conditions. Physiological (natural) causes include pregnancy and breastfeeding, which raise prolactin substantially. Beyond this, emotional or physical stress, sleep, and the natural variation through the day can all shift the level. A prolactinoma — a benign tumour of the pituitary gland that produces prolactin — is the most common pathological (medical) cause of a significantly raised level.
When to act
A markedly raised prolactin is worth raising with your GP, particularly if you are experiencing symptoms such as milk production, irregular periods, or visual changes. A mildly raised result — especially if there is no obvious cause — will often be repeated first, since the blood-draw stress alone can be responsible. Your GP will consider the medicines you take, the degree of the elevation, your symptoms, and whether any further testing is worth considering. Your GP may, for example, look at thyroid function or arrange imaging, depending on your picture. Most causes of raised prolactin are benign and well understood once the picture is put together. This page is general information and is not a substitute for advice from your GP.
Frequently asked questions
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