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Endocrinology

Prolactinoma

Most common functioning pituitary adenoma. Excess prolactin causes hypogonadism, galactorrhoea and, for macroadenomas, mass effects (headache, bitemporal hemianopia).

Last reviewed 30 Jun 2026 - MedicoMedics editorial team

Prolactin mechanism of action and lactotroph adenoma

Pathophysiology

Lactotroph adenoma autonomously secretes prolactin, suppressing GnRH pulsatility and thus LH/FSH - hypogonadotrophic hypogonadism. Stalk-effect hyperprolactinaemia occurs when non-secreting sellar masses interrupt dopaminergic inhibition.

Sources: Endocrine Society CPG Hyperprolactinemia (J Clin Endocrinol Metab 2011;96:273); Pituitary Society Consensus on Prolactinomas (Lancet Diabetes Endocrinol 2023;11:722)

Clinical presentation

Women: oligomenorrhoea/amenorrhoea, infertility, galactorrhoea. Men: erectile dysfunction, reduced libido, gynaecomastia, infertility. Macroadenoma: headache, visual field defects, hypopituitarism.

Sources: Endocrine Society CPG Hyperprolactinemia (J Clin Endocrinol Metab 2011;96:273); Pituitary Society Consensus on Prolactinomas (Lancet Diabetes Endocrinol 2023;11:722)

Diagnosis

Confirm elevated prolactin, exclude pregnancy, primary hypothyroidism, renal failure, and drugs (antipsychotics, metoclopramide, opioids, oestrogens). Prolactin >200 mcg/L strongly suggests prolactinoma. MRI pituitary defines size; formal visual fields for macroadenomas. Dilute samples to exclude hook effect.

Sources: Endocrine Society CPG Hyperprolactinemia (J Clin Endocrinol Metab 2011;96:273); Pituitary Society Consensus on Prolactinomas (Lancet Diabetes Endocrinol 2023;11:722)

Management

Dopamine agonists first-line - cabergoline preferred (better tolerated, shrinks tumour in >80%). Transsphenoidal surgery for intolerance, resistance, or CSF leak. Radiotherapy reserved for refractory disease.

Sources: Endocrine Society CPG Hyperprolactinemia (J Clin Endocrinol Metab 2011;96:273); Pituitary Society Consensus on Prolactinomas (Lancet Diabetes Endocrinol 2023;11:722)

Sample USMLE-style MCQs

Try 5 questions on this topic. Practice hundreds more free with a trial.

Question 1

First-line therapy for prolactinoma?

Question 2

Which drug commonly causes hyperprolactinaemia?

Question 3

A 30-year-old woman has amenorrhoea and galactorrhoea; prolactin 15 mcg/L, MRI shows 2 cm sellar mass. Suspect?

Question 4

Which lab must be checked before diagnosing prolactinoma?

Question 5

Prolactin causes infertility mainly by?

References

Primary guidelines and peer-reviewed sources used for this entry. Reviewed 30 Jun 2026 by MedicoMedics editorial team.

  1. Endocrine Society CPG Hyperprolactinemia (J Clin Endocrinol Metab 2011;96:273)
  2. Pituitary Society Consensus on Prolactinomas (Lancet Diabetes Endocrinol 2023;11:722)

Frequently asked

Which drug causes drug-induced hyperprolactinaemia?

Dopamine antagonists such as risperidone, haloperidol, metoclopramide, and antiemetics.

What is the hook effect?

Very high prolactin saturates the immunoassay and falsely reports a low value; dilute the sample if a macroadenoma has surprisingly normal prolactin.

Why does prolactin cause hypogonadism?

It suppresses hypothalamic GnRH, reducing LH/FSH and gonadal steroidogenesis.

Is cabergoline safe in pregnancy?

Usually stopped once pregnancy confirmed for microadenomas; continued cautiously for macroadenomas with vision monitoring.

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