What is prolactin?
Prolactin is a hormone made by the anterior pituitary gland, located at the base of the brain. Its primary function is to stimulate and maintain breast milk production (lactation) after childbirth. In men and non-pregnant women, prolactin is present in small amounts. Levels naturally rise during pregnancy and breastfeeding. Elevated prolactin (hyperprolactinaemia) outside of pregnancy suppresses reproductive hormones, causing infertility and other symptoms.
Prolactin normal range
| Group | Normal Range (ng/mL or mIU/L) |
|---|---|
| Non-pregnant women | 2 – 29 ng/mL |
| Men | 2 – 18 ng/mL |
| Pregnant women | 10 – 209 ng/mL (varies by trimester) |
| Breastfeeding women | Up to 300 ng/mL |
HIGH Prolactin — Hyperprolactinaemia
Causes: prolactinoma (a benign pituitary tumour that overproduces prolactin — the most common cause of pathological elevation), medications (antipsychotics, metoclopramide, domperidone, some antidepressants, opioids, antihypertensives like methyldopa and verapamil), hypothyroidism (high TRH stimulates prolactin release), kidney disease (reduced clearance), liver cirrhosis, chest wall injury or breast stimulation. Symptoms in women: irregular or absent periods (amenorrhoea), milky nipple discharge (galactorrhoea) unrelated to breastfeeding, infertility, decreased libido. Symptoms in men: reduced libido, erectile dysfunction, infertility, gynecomastia (breast tissue growth). Very large prolactinomas can compress the optic chiasm causing visual field loss.
When is a pituitary MRI needed?
A prolactin level above 100 ng/mL strongly suggests a prolactinoma and warrants a pituitary MRI to look for a tumour. Levels of 25–100 ng/mL can have many causes (medications, hypothyroidism, stress) and are investigated based on clinical context. Very high levels (>500 ng/mL) almost always indicate a large prolactinoma (macroprolactinoma).
Treatment of prolactinoma
Most prolactinomas are treated with dopamine agonist medications — cabergoline or bromocriptine — which are highly effective at lowering prolactin and shrinking the tumour. Surgery is rarely needed. Regular prolactin monitoring is used to track treatment response.
Questions to ask your doctor
- Should I have a pituitary MRI?
- Is a medication causing my high prolactin?
- Should I check my thyroid (TSH)?
- Can high prolactin be treated with medication alone?
- Will my fertility return once prolactin is normalised?