Understanding hyperprolactinaemia in women

Hyperprolactinaemia means there is more of the hormone prolactin in your blood than there should be. Prolactin is best known for making breast milk, so it is normal for levels to be high during pregnancy and breastfeeding. Outside those times, though, raised prolactin is one of the most common hormonal reasons a woman’s periods become irregular or stop, ovulation falters, fertility drops, and the vagina becomes dry and uncomfortable.¹

In most cases it is not dangerous and it is very treatable. But because high prolactin can quietly switch off the rest of your reproductive hormones, it is worth understanding what it is, what causes it, and what to do about it.¹

In our experience, when vaginal dryness and irregular periods show up together in a woman who’s nowhere near menopause, it’s worth asking what’s happening higher up the hormonal chain – and prolactin sits high on that list of blood tests that quickly give us good information to work with.

What is hyperprolactinaemia?

Prolactin is made by the pituitary gland, a pea-sized gland at the base of the brain, in cells called lactotrophs.² Its main job is to stimulate breast milk production after birth, but prolactin receptors sit all over the body, including the ovaries, breast, liver, kidneys, adrenal glands and brain, so it influences far more than lactation alone.²

Prolactin is unusual among hormones because the brain mostly holds it down rather than driving it up. Dopamine, produced in the hypothalamus, continuously tells the pituitary to keep prolactin low. Anything that interrupts that dopamine signal allows prolactin to climb.³

Reference ranges vary between laboratories, but in non-pregnant women a level below roughly 25 micrograms per litre (about 500 mU/L) is generally considered normal. Mildly raised results are common and often have a simple explanation, while very high levels point more strongly towards a prolactin-producing tumour.¹

Who gets it, and how common is it?

Hyperprolactinaemia turns up most often in women during the reproductive years, between the late teens and the forties, which is exactly when changes to periods and fertility are most noticeable.³ Prolactinomas, the most frequent underlying tumour, are several times more common in women than in men, partly because the menstrual changes they cause tend to send women to a doctor sooner, while they are smaller.⁴

It is also common enough that it sits on the standard list of things to check whenever periods stop, fertility stalls, or there is unexplained milky discharge, rather than being a rare or exotic diagnosis.⁵

What are the symptoms in women?

High prolactin lowers oestrogen by suppressing the hormones that drive the ovaries, so most symptoms in women come back to low oestrogen and absent ovulation.¹ The most common are:

• Periods that stop altogether (secondary amenorrhoea) or become infrequent and irregular (oligomenorrhoea)
• Trouble conceiving, because ovulation is not happening reliably
• Milky nipple discharge when not pregnant or breastfeeding (galactorrhoea)
• Vaginal dryness, painful sex and reduced libido from low oestrogen
• Low mood, irritability and changes in wellbeing
• Bone thinning over time, particularly when periods have been absent for a while

The vaginal symptoms deserve a special mention, because they are easy to misread. Persistent vaginal dryness, irritation and pain with sex in a woman who is not yet menopausal can be a sign that oestrogen has dropped, and raised prolactin is one of the hormonal reasons that can happen.¹

Because irregular or absent periods have several possible causes, hyperprolactinaemia is usually considered alongside others such as polycystic ovary syndrome and thyroid problems, and the blood tests are chosen to tell them apart.⁵

Some women have no symptoms at all, and the high prolactin is picked up by chance on a blood test done for another reason.³

When the cause is a tumour

If the high prolactin is being driven by a larger pituitary tumour, the tumour itself can press on nearby structures and cause headaches or vision problems, because the nerves that carry sight pass very close to the pituitary gland.⁴ Any new persistent headache or change in your vision alongside menstrual changes is a reason to be seen promptly.

What causes high prolactin in women?

Causes range from completely harmless and temporary, through medications, to genuine pituitary problems. Working out which one you have is the whole point of the diagnostic process, because the treatment is entirely different for each.¹

Everyday and temporary causes

Prolactin naturally rises with pregnancy and breastfeeding, but also briefly after nipple stimulation, sex and orgasm, exercise, a meal, stress and even a stressful blood draw.³ Because of this, a single mildly raised result is often repeated under calmer, fasting conditions before anyone reads too much into it.

An underactive thyroid

An underactive thyroid (hypothyroidism) is a classic and easily missed cause. When the thyroid is sluggish, the body produces more thyrotropin-releasing hormone, which also nudges the pituitary to make prolactin, so prolactin drifts up.³ This is why a thyroid blood test is part of the standard work-up, and why correcting the thyroid often fixes the prolactin without any other treatment.

Medications

Many medicines raise prolactin, usually by blocking dopamine. The common culprits include antipsychotics and some older antidepressants, anti-nausea and reflux drugs such as metoclopramide, certain blood pressure medicines, opioids and high-dose oestrogen.³ Drug-induced hyperprolactinaemia is one of the most frequent causes, and it is important never to stop a prescribed medicine on your own; the change is always made with your prescriber.

Prolactinoma and other pituitary issues

The most common pathological cause is a prolactinoma, a benign (non-cancerous) prolactin-producing growth on the pituitary gland.⁴ Other masses near the pituitary, or conditions that interfere with the dopamine signal travelling down to it, can raise prolactin too. Kidney and liver disease can also play a part.³

Macroprolactin and idiopathic cases

Sometimes the blood carries a large, inactive form of prolactin called macroprolactin. It shows up on the test as a high result but causes no symptoms, a situation sometimes called pseudo-hyperprolactinaemia, and it accounts for a meaningful share of raised results.² When no cause can be found despite a thorough search, the condition is labelled idiopathic, meaning the reason is simply not known.¹

The brain–ovary connection

To understand why high prolactin stops periods, it helps to picture the chain of command that runs your cycle, the hypothalamic–pituitary–ovarian axis (you can read more about the HPO and HPA axes on the site).

Normally the hypothalamus releases gonadotrophin-releasing hormone in pulses, which prompts the pituitary to release follicle-stimulating hormone and luteinising hormone, which in turn tell the ovaries to grow follicles, ovulate and make oestrogen. Excess prolactin interferes with those pulses, so the whole chain downstream quietens, oestrogen falls, ovulation stops, and periods become irregular or disappear.¹

This is also why hyperprolactinaemia can look so similar to other causes of absent periods, such as hypothalamic amenorrhoea or relative oestrogen deficiency, and why a prolactin test is part of investigating any unexplained loss of periods.⁵

Prolactinoma, the most common cause

Prolactinomas are the commonest hormone-producing pituitary tumours, and they are far more common in women than men.⁴ They are graded by size: a microprolactinoma is under 10 millimetres, and a macroprolactinoma is 10 millimetres or larger.

Most prolactinomas in women are small. They behave well, respond to medication, and very often shrink. The larger ones matter not only for the prolactin they produce but for the space they take up, which is what causes headaches and visual changes.⁴ Because oestrogen can stimulate these growths and dopamine inhibits them, the treatment we use is built around restoring that dopamine brake.⁴

How is it diagnosed?

Diagnosis starts with a simple blood test measuring prolactin, often repeated to avoid being caught out by a temporary spike.¹ From there, the work-up is really about finding the cause rather than just confirming the number.

A careful medication review comes first, since drug-induced cases are so common.³ Pregnancy is ruled out, a thyroid test checks for an underactive thyroid, and kidney and liver function are considered. If the level is high and unexplained, or symptoms suggest a tumour, an MRI scan of the pituitary is the next step.¹

Two laboratory traps worth knowing about

Two quirks of the blood test can mislead, and a good laboratory accounts for both. The first is macroprolactin, the inactive form that produces a high reading without symptoms; checking for it avoids treating a number that does not need treating.² The second is the hook effect, where a very large tumour produces so much prolactin that the assay paradoxically reports a falsely low result; diluting the sample reveals the true, very high level.² If your result and your symptoms do not seem to match, these are worth raising.

How is it treated?

Treatment depends entirely on the cause, and not every case needs treating. A woman with a small prolactinoma, normal periods and no troublesome symptoms may simply be monitored.¹ When treatment is needed, the approach falls into a few clear paths.

Dopamine agonist medication

For prolactinomas and idiopathic hyperprolactinaemia, the first-line treatment is a class of medicines called dopamine agonists, which restore the brain’s natural brake on prolactin. They lower prolactin, shrink the tumour and restore normal cycles in the large majority of women.⁴ The most commonly used agent works well at a low weekly dose and is generally better tolerated than the older alternative.⁵

After a sustained period of normal prolactin and a tumour that has shrunk or disappeared, it is sometimes possible to reduce or stop the medication under specialist supervision, with ongoing monitoring because levels can rise again.⁴

Treating the underlying cause

Where the trigger is something else, the fix follows the cause. An underactive thyroid is treated with thyroid hormone, which usually brings prolactin back down on its own.³ For medication-induced cases, the prescriber may switch to an alternative drug that does not raise prolactin, where a suitable one exists, rather than reaching for a dopamine agonist.⁵ This is the functional-medicine instinct we apply throughout: correct the thing driving the problem, and the downstream hormone picture tends to settle.

When surgery or other options are needed

A minority of tumours do not respond to medication or cause intolerable side effects. In those cases, surgery to remove the tumour, performed at an experienced specialist centre, is the next option, and radiation is reserved for the rare aggressive tumours that resist both.⁴

Fertility and pregnancy

Because high prolactin blocks ovulation, it is a treatable cause of infertility, and this is often the reason a woman is first investigated.⁵ Restoring normal prolactin with a dopamine agonist usually brings ovulation and fertility back, and many women conceive once their levels are controlled.⁵

Management around pregnancy is individual and specialist-led, because the approach to medication and tumour monitoring shifts once you are pregnant, and the risk of a small tumour growing during pregnancy is low.⁴ If you have hyperprolactinaemia and are planning a pregnancy, this is a conversation to have with your specialist in advance.

Bones and long-term health

The low oestrogen that comes with long-standing, untreated hyperprolactinaemia is the real concern for bone health. Oestrogen protects bone, so when periods have been absent for a long time, bone density can fall, raising the risk of osteopenia and osteoporosis later on.⁶ Treating the high prolactin and restoring oestrogen is the main way to protect the skeleton, which is one of the reasons it is worth addressing even when symptoms feel manageable.⁶

What about perimenopause and menopause?

Hyperprolactinaemia is most often diagnosed during the reproductive years, but it does not vanish with age. Symptoms such as irregular periods and vaginal dryness can blur with the ordinary changes of perimenopause and menopause, which makes a raised prolactin easy to overlook.³ If menstrual changes or galactorrhoea seem out of step with what you would expect for your stage of life, prolactin is still worth checking.

Frequently asked questions

Is hyperprolactinaemia dangerous?

For most women it is not dangerous and responds well to treatment. The things that need attention are the effects of long-term low oestrogen on bone, and, in the smaller number of cases caused by a larger tumour, pressure on nearby structures.¹

Can high prolactin stop my periods?

Yes. It is one of the more common hormonal reasons periods become irregular or stop, because it suppresses the hormones that drive ovulation. Periods usually return once prolactin is brought back to normal.¹

Will it stop me getting pregnant?

It can make conceiving difficult while levels are high because ovulation is blocked, but it is a treatable cause of infertility. Most women regain normal fertility once prolactin is controlled.⁵

Why am I leaking milk when I’m not pregnant?

Milky discharge outside pregnancy or breastfeeding (galactorrhoea) is a classic sign of raised prolactin, since prolactin’s day job is making milk. It is worth a prolactin blood test to check.³

Does stress cause high prolactin?

Stress, including the stress of a blood test, can briefly raise prolactin, which is why a single mildly high result is often repeated under calmer conditions before anyone acts on it.³

My prolactin is high but I feel fine. Do I need treatment?

Not always. If the cause turns out to be macroprolactin, the inactive form, or a small tumour with no symptoms and normal periods, monitoring may be all that is needed rather than active treatment.²

Can a medication be causing it?

Very commonly, yes, especially antipsychotics, some antidepressants, reflux and anti-nausea drugs, and certain blood pressure medicines. Never stop a prescribed medicine yourself; any change is made with your prescriber.³

Does a high result mean I have a brain tumour?

Not necessarily. Many cases are due to medication, an underactive thyroid, macroprolactin or a temporary spike. A prolactinoma is the most common pathological cause, but it is benign and treatable; very high levels make it more likely and prompt an MRI.¹

What to do next

If your periods have changed or stopped, you are struggling to conceive, you notice milky discharge, or you have unexplained vaginal dryness and low libido, a prolactin blood test is a sensible early step. Our guide to how to get hormone and blood testing walks through how to arrange it, and it is worth pairing prolactin with a thyroid check given how often the two are linked.

Because high prolactin sits at the top of the hormonal chain, it is best worked up and managed with a clinician rather than self-treated. If you would like to talk it through first, Aunt Vadge’s Assistant chat widget is in the bottom-left of the screen, and our practitioners are here if you want a more thorough, whole-person look at what might be driving your symptoms.

This article is general information and not a substitute for personalised medical advice. Please speak with a qualified health practitioner about your individual situation. Last reviewed June 2026.