A prolactin above the reference range is far from always a pituitary growth. Medication, stress around the blood draw and an underactive thyroid together explain a large share of raised results. In women the value is usually requested because of a cycle that stalls, milky discharge, or difficulty conceiving.
What I find unhelpful about most pages on this: they jump straight to the prolactinoma. That is the rarest of the eight and the only one that frightens people.
Below they are ordered by how often they occur, followed by the part no Dutch consumer page carries: why a single high result often says nothing yet.
What does prolactin actually do?
Prolactin is made in your pituitary, the small gland under your brain. Its best known job is milk production after birth. At high levels prolactin also suppresses the hormones that drive your ovulation, which is exactly why your cycle responds to it. Which hormone actually triggers that ovulation is covered in LH levels.
That brake is a normal mechanism. During breastfeeding it holds your cycle still for a while, and that is functional.
Outside that period a high value signals something else is going on.
1. Medication
This is the most common cause of raised prolactin outside pregnancy, and also the easiest to check. Drugs that block or lower dopamine remove the natural brake on prolactin.
With antipsychotics this happens in a substantial share of users, with clear differences between individual drugs (PMID 32243999). Some antidepressants, anti-nausea drugs and blood pressure medicines are also known for it.
| Group | Examples | How often prolactin rises |
|---|---|---|
| Antipsychotics | risperidone, amisulpride, haloperidol | Often, sometimes markedly |
| Anti-nausea drugs | metoclopramide, domperidone | Often |
| Antidepressants | some SSRIs and tricyclics | Sometimes, usually mild |
| Oestrogen-containing contraception | combined pill | Sometimes, usually mild |
| Opioids | morphine, tramadol | Sometimes |
The Dutch Farmacotherapeutisch Kompas lists this effect per drug. Bring your medication list to the appointment and this is checked within a minute. Never stop a prescribed drug yourself to lower a value.
2. Pregnancy and breastfeeding
During pregnancy prolactin climbs steadily to a multiple of the normal value. After birth it stays high for as long as you feed.
That is why a pregnancy test comes first here too. A raised prolactin in a pregnant woman is an expected finding, not an abnormality.
3. An underactive thyroid
With an underactive thyroid, TRH rises, and TRH stimulates not only your thyroid but your prolactin as well. So you get two abnormal values with one shared cause.
That is why TSH is nearly always drawn alongside a raised prolactin. When the thyroid is treated, prolactin often normalises behind it. How to read that result is in thyroid values explained.
4. Stress around the blood draw
Prolactin responds to acute stress, and needle anxiety counts. A physically demanding morning, poor sleep or breast stimulation can also push the value up briefly.
That rise is usually modest, but with a value just above the upper limit it can make the difference. This is why a mildly raised result is often simply repeated.
5. Prolactinoma
This is a benign pituitary growth that produces prolactin itself. It is the best known cause and not the most common one.
Here the height of the value gives direction. Values far above ten times the upper limit fit a prolactinoma better than medication or stress (PMID 21296991). Headache with a change in your visual field always warrants prompt contact with your GP.
6. Other pituitary causes
A growth that makes no prolactin itself can compress the stalk to the pituitary. Dopamine then no longer reaches the cells, the brake falls away and prolactin rises mildly to moderately.
Telling this apart from a prolactinoma matters clinically and is done with imaging, not with blood.
7. PCOS
In PCOS a mildly raised prolactin is sometimes found. Whether that is causal or simply co-occurring has not been settled.
In practice it means a mildly raised value in a woman with a long cycle and signs of androgen excess is not automatically the explanation. See PCOS testing.
8. Kidney and liver conditions
With severely reduced kidney function, prolactin is cleared more slowly and accumulates. Advanced liver disease does something similar.
These two sit at the bottom because they are rarely the first suspicion. They do explain why kidney values often sit in the same panel.
Why does a single result often say nothing?
Because part of the measured prolactin is not active at all. Prolactin can bind to an antibody, forming a large complex called macroprolactin. The laboratory assay counts it in, but the complex does not reach your tissue and so causes no symptoms.
In a share of raised results this turns out to be the entire explanation (PMID 15949152). Laboratories can demonstrate it with a simple pre-treatment step, and in the Netherlands that is by no means always done as standard (PMID 23304187).
Take two women who both come back with a prolactin of 900 mIU/l. One has had a stalling cycle for a year plus milky discharge. The other has a normal cycle and no symptoms at all. In the second, macroprolactin is a realistic explanation, and without that extra step she risks an MRI that finds nothing.
This is the piece I cannot find on any Dutch consumer page, while it is exactly what separates repeating the test from referring onward. Feel free to ask about it when a result does not match your symptoms.
Which symptoms fit a high prolactin?
In women, cycle changes come first: a longer cycle, a cycle that stops, or difficulty conceiving. Milky nipple discharge occurs but is often absent. Lower sex drive, vaginal dryness and headache are also reported.
If your cycle stops altogether, amenorrhoea is the wider overview. For the libido side see low sex drive.
Symptoms that justify prompt contact are new or changing headache and loss in your visual field, especially at the outer edges. That combination fits pressure on the optic chiasm and does not wait for a check in three months.
How can you prepare for the blood draw?
Fasting is not needed. What helps: book the draw at a calm moment, avoid heavy exertion and breast stimulation in the hours before, and sit still for fifteen minutes before the needle.
Cycle day matters little for prolactin, unlike oestradiol and progesterone. If you still menstruate you can simply combine it with the rest of your hormone profile.
The background on the value itself is on prolactin. Which hormones together give a usable picture is in hormone testing in women, and hormones for women fits alongside it.
Always discuss an abnormal result with your GP. Thuisarts describes the route that follows, and it nearly always begins with repeating before any imaging is involved.
References
- Melmed S, Casanueva FF, Hoffman AR, et al. Diagnosis and treatment of hyperprolactinemia: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96(2):273-288. PMID 21296991.
- Gonzalez-Rodriguez A, Labad J, Seeman MV. Antipsychotic-induced hyperprolactinemia in aging populations: prevalence, implications, prevention and management. Prog Neuropsychopharmacol Biol Psychiatry. 2020;101:109941. PMID 32243999.
- Fahie-Wilson MN, John R, Ellis AR. Macroprolactin; high molecular mass forms of circulating prolactin. Ann Clin Biochem. 2005;42(Pt 3):175-192. PMID 15949152.
- Shimatsu A, Hattori N. Macroprolactinemia: diagnostic, clinical, and pathogenic significance. Clin Dev Immunol. 2012;2012:167132. PMID 23304187.
- Farmacotherapeutisch Kompas. Medicines and hyperprolactinaemia. Available via farmacotherapeutischkompas.nl.
- Thuisarts. I have an abnormal blood test result. Available via thuisarts.nl.
Every blood test result at Lunara includes a professional assessment by a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
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