Reasoning GP · Algorithm · 1-page summary
Raised prolactin (hyperprolactinaemia)
For: adults with a raised prolactin, or galactorrhoea, amenorrhoea or oligomenorrhoea, low libido or ED, in primary care. Not for: cabergoline titration, withdrawal trials or prolactinoma in pregnancy (endocrinology leads; do not measure prolactin in pregnancy).
Core rule: exclude a stressed sample, pregnancy, hypothyroidism, drugs, renal or liver disease and macroprolactin before imaging — but a new visual-field defect or a sudden severe headache never waits for those tests.
0Stop — call 999 now — possible pituitary apoplexy
- Sudden severe (thunderclap) headache with a known pituitary adenoma, or with visual disturbance, double vision, vomiting, collapse or altered consciousness — even with no known pituitary disease (often the first presentation) → 999 / A&E. It can mimic subarachnoid haemorrhage.
- While waiting: if adrenal insufficiency is suspected or the patient is unstable → hydrocortisone 100 mg parenterally per the emergency protocol. Do not delay transfer.
1Triage — what does this result need?
| Finding | Action |
|---|---|
| New field defect | Raised prolactin + new visual-field defect, with or without headache → Same-day specialist / emergency |
| Markedly raised | Or unexplained persistent rise, significant symptoms or hypogonadism → Urgent endocrinology |
| Mild / unexpected | Repeat rested, preferably ≥2 h after waking; no exercise, sex or breast examination first; cannula if venepuncture stress. Fasting not needed. |
| Disproportionate | Raised with no symptoms, or out of proportion to them → macroprolactin (PEG); read by the lab's criteria |
2Screen — one row is enough
- Visual or cranial nerve symptoms, significant or progressive headache, hypopituitarism → Urgent endocrine advice ± MRI
- Prolactin >5000 mIU/L, no drug cause → strongly suggests prolactinoma → Urgent endocrinology
- On an antipsychotic, prolactin >2000 mIU/L, symptomatic or rising (local trigger) → Urgent endocrine / psychiatry discussion
- Pregnant with a macroprolactinoma or tumour near the chiasm → Urgent endocrinology
- Aged ≥50, discharge, retraction or other change in one nipple only → Suspected cancer pathway (NG12), whatever the prolactin. Under 50: local breast pathway.
- Pituitary mass with a modest prolactin → ask the lab to dilute (hook effect).
3Assess — before any imaging
☐ Visual fields (confrontation screens only; formal perimetry where indicated), eye movements, neurology ☐ Pregnancy test ☐ TSH ± free T4 ☐ Renal and liver function ☐ Full medicine and recreational drug review ☐ Pituitary function if a lesion is suspected
Use the lab's sex-specific range and units. Not in primary care: MRI for a single mildly raised result; repeated breast stimulation.
4Classify — only if the screen is negative
- Physiological — pregnancy, lactation, stress, sex, nipple stimulation → repeat rested.
- Macroprolactin — PEG positive, normal monomeric prolactin, no symptoms or visual, neurological or pituitary signs → reassure, explain, discharge.
- Drugs (commonest pathological) — antipsychotics, metoclopramide, domperidone, SSRIs, opioids, methyldopa, verapamil → prescriber review.
- Systemic — hypothyroidism (TSH first), CKD, cirrhosis, PCOS, chest-wall injury or zoster.
- Prolactinoma or stalk compression — unexplained persistent rise → endocrine advice ± MRI.
- Uncertain — still raised after medication review → endocrine advice ± MRI; do not blame the drug.
5Treat today — only these
- Drug cause: discuss stopping, reducing or switching with the prescriber where safe; repeat after the agreed interval. Never stop an antipsychotic without the mental-health team; no empirical dopamine agonist.
- Hypothyroidism: treat it; prolactin normalises.
- On cabergoline (specialist-initiated): check BP, adherence, impulse-control, psychiatric effects and sleepiness; never change the dose or stop it without specialist advice. Doses: NICE/SPC, BNF, local formulary.
- Driving: visual-field defect → do not drive, notify DVLA; cabergoline sleepiness → do not drive if affected. Document it.
6Refer routinely
- Microprolactinoma on MRI; complex macroprolactin or persistent monomeric rise → endocrinology.
- Symptomatic drug-induced rise, drug cannot change → endocrinology; antipsychotic → psychiatry (any switch is their decision).
- Prolonged hypogonadism or amenorrhoea → fracture-risk assessment. Planning pregnancy on cabergoline → endocrinology.
7Never reassure by
- No known pituitary disease, when a sudden severe headache comes with visual signs.
- Normal confrontation fields — they only screen.
- A convincing drug cause, when prolactin stays raised after review.
- A modest prolactin with a pituitary mass (hook effect or stalk compression).
- "It's just prolactin" when one nipple changes at ≥50.
- The prolactin level alone — it does not reliably predict symptom severity.
8Safety-net — say it, then document it
999 “Call 999 for a sudden, severe headache, especially with loss of vision, double vision, vomiting, collapse or confusion.” Same day “Any new blurring or loss of side vision — contact us today.” Within a week “If the discharge becomes one-sided or bloodstained, or the nipple pulls in, contact the practice within a week.”
On cabergoline: “Tell us about urges to gamble, spend or binge, mood change or sudden sleepiness — and don't drive if sleepy.” Macroprolactin: explain it in plain words so the patient does not feel dismissed.
✓Safe to leave primary care only if — all five, documented
No block 0–2 row applies
Visual fields recorded; driving advice given
Rested repeat, pregnancy, TSH, U&E, LFTs and drugs checked
Macroprolactin read by lab criteria; cause named or uncertainty stated
Safety-net given; recheck owner and date set
Summary of the full Reasoning GP hyperprolactinaemia algorithm, which holds the causes, cabergoline, pregnancy, bone and monitoring detail. Sources: Endocrine Society 2011; Pituitary Society 2023; NICE NG12 (updated April 2026), NG257; SfE pituitary apoplexy; SfE/BSE/BHVS echocardiography; MHRA; DVLA; local shared care. No UK national guideline covers hyperprolactinaemia. Clinical reference — local endocrinology pathways take precedence.