My prolactin is high. What happens next?

High prolactin is common and most of it is not a pituitary tumour. Prolactin rises with stress, sleep, meals, nipple stimulation, chest wall irritation, exercise and a long list of medications. The 2023 Pituitary Society international consensus statement advises that patients with prolactin levels below five times the upper limit of normal should have repeat prolactin testing before further workup. A single abnormal result is a reason to retest, not to image.

What is checked before imaging

Four things account for most confirmed elevations that are not prolactinomas. Medications come first: antipsychotics, metoclopramide, some antidepressants and other dopamine blockers. Pregnancy is excluded. Primary hypothyroidism raises prolactin and is corrected before anything else is done. Chronic kidney disease and liver disease reduce clearance. Macroprolactin, an inactive antibody-bound form that assays still detect, is checked when the level is moderately raised, usually under 200 ng/mL, and particularly when the person has no symptoms at all.

When an MRI is needed

Once hyperprolactinaemia is confirmed and secondary causes have been excluded, a pituitary MRI is performed. The consensus notes that adenoma size and prolactin level generally correlate, and that a prolactin above 200 ng/mL points more strongly to a true prolactinoma than to another cause. There is one important trap in the other direction: in a large pituitary mass with typical symptoms but a normal or only mildly raised prolactin, the laboratory should be asked for a 1:100 dilution to exclude the high-dose hook effect, an assay artefact that reports a falsely low value.

Treatment if a prolactinoma is found

Most prolactinomas are treated with medication rather than surgery. Cabergoline is the preferred dopamine agonist because it is more effective and better tolerated than bromocriptine, with typical doses of 0.5 to 3.5 mg per week. Treatment aims to normalise prolactin, restore periods and fertility, protect bone, and shrink the tumour. Not every small prolactinoma needs treating: an asymptomatic microadenoma with normal gonadal function can sometimes be monitored.

Before your repeat test, take the sample in a relaxed state, avoid nipple stimulation and vigorous exercise beforehand, and bring a full medication list including over the counter products. Ask whether macroprolactin was checked if your level is moderately raised and you have no symptoms.