Examqo › Examqo library › Internal medicine › Endocrinology and diabetes · IMLE
Hyperprolactinaemia and pituitary tumours
Before diagnosing a prolactinoma, exclude pregnancy, drugs and hypothyroidism; a prolactinoma is treated with a drug first — cabergoline — even when it is large and threatens vision, with surgery reserved for failure or intolerance.
Why it matters in the exam
Questions present a woman with amenorrhoea, galactorrhoea and infertility, or a man with low libido and erectile problems and, later, a visual field defect (bitemporal hemianopia). The first step is a pregnancy test; then drugs that raise prolactin (antipsychotics — especially risperidone — metoclopramide, domperidone), primary hypothyroidism (TRH stimulates prolactin) and kidney failure. A very high value (above about 200 ng/mL) points to a secreting macroadenoma, while a moderate value with a large tumour points to stalk compression or the "hook effect" — in that case the laboratory is asked to dilute the sample.
Further questions deal with pituitary tumours in general. An incidental pituitary finding needs hormone testing for hypersecretion (prolactin, IGF-1 for acromegaly, a Cushing screen), and a macroadenoma (10 mm or more) also needs testing for hormone deficiency and visual fields. Pituitary apoplexy — sudden headache, falling vision and ocular nerve palsy — calls for immediate hydrocortisone and neurosurgical assessment. In acromegaly the first test is IGF-1, confirmed by failure of GH suppression on a glucose load.
Key points
- Exclude pregnancy, drugs, hypothyroidism and kidney failure.
- Prolactin above 200 ng/mL points to a secreting macroadenoma.
- Cabergoline is first-line, even with visual loss.
- Macroadenoma 10 mm or more: hormone deficiencies and visual fields.
- Apoplexy: hydrocortisone at once; acromegaly: IGF-1.
Summary table
| Situation | Clue | Test | Treatment |
|---|---|---|---|
| Non-tumour causes | Pregnancy, antipsychotics, metoclopramide, hypothyroidism, CKD | Pregnancy test, TSH, creatinine | Treat the cause or change the drug |
| Prolactinoma | Amenorrhoea, galactorrhoea, low libido | Prolactin (above 200 ng/mL points to macroadenoma), MRI | Cabergoline — even with visual loss |
| Hook effect | Large tumour with moderate prolactin | Dilute the sample | Prevents a wrong diagnosis |
| Incidental finding | Pituitary mass on MRI | Prolactin, IGF-1, Cushing screen | Macroadenoma 10 mm or more: deficiencies and visual fields |
| Apoplexy | Sudden headache, falling vision, ocular nerve palsy | MRI | Hydrocortisone at once and a neurosurgeon |
| Acromegaly | Enlarged hands and feet, jaw, diabetes, hypertension | IGF-1; GH not suppressed by a glucose load | Transsphenoidal surgery |
In the full version for subscribers
- A simple algorithm
- Memory aid
- Exam traps
- 5 review cards
- Enough for IMLE
The full version is open to subscribers of: Medical licensing exam (IMLE), Internal medicine, Obstetrics and gynecology, Neurology, Family medicine, Neurosurgery, Diagnostic pathology, Psychiatry.
Subscriber? Read the full topic Plans and prices 25 free questions
Sources
- Endocrine Society Clinical Practice Guideline: Diagnosis and Treatment of Hyperprolactinemia, 2011 — Causes, macroprolactin, hook effect and dopamine agonists
- Pituitary Society international consensus on the diagnosis and management of prolactin-secreting adenomas, 2023 — Cabergoline first-line therapy
- Harrison's Principles of Internal Medicine, 21st edition (2022) — Hypopituitarism; Pituitary Tumor Syndromes
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.