Summary

Prolactinoma is a benign pituitary adenoma that secretes prolactin. It is the most common functioning pituitary tumour, accounting for ~40% of all pituitary adenomas. Prolactinomas are classified by size: microprolactinomas (<10mm) and macroprolactinomas (≥10mm). Women typically present with amenorrhoea, galactorrhoea, and infertility, whereas men often present later with erectile dysfunction and mass effects (visual field defects, headache). The key investigation is serum prolactin — levels correlate with tumour size. First-line treatment is dopamine agonists (cabergoline or bromocriptine), which shrink most tumours. Surgery is reserved for drug-resistant cases or acute visual compromise.

Key Facts

• Definition: Prolactin-secreting pituitary adenoma
• Classification: Microprolactinoma (<10mm), Macroprolactinoma (≥10mm)
• Presenting Features: Galactorrhoea, Amenorrhoea, Infertility, Erectile dysfunction
• Prolactin Level: >5000 mU/L usually indicates macroprolactinoma
• Treatment: Dopamine agonists (Cabergoline > Bromocriptine)
• Surgery: Rarely needed; For drug-resistant or visual compromise

Clinical Pearls

"Prolactin Level Correlates with Size": Very high prolactin (>5000 mU/L) = Large tumour. Be suspicious of non-functioning adenoma with stalk effect if large tumour but only mild elevation.

"The Hook Effect": Very high prolactin levels can paradoxically appear low due to assay saturation — request serial dilution if suspected.

"Drugs First": Unlike most pituitary tumours, prolactinomas are treated medically first. Dopamine agonists shrink the tumour in >80%.

"Exclude Other Causes": Always exclude pregnancy, drugs (antipsychotics, metoclopramide), hypothyroidism, and stalk compression before diagnosing prolactinoma.

General

• Galactorrhoea (examine for nipple discharge)
• Gynecomastia (men)

Visual Fields

• Bitemporal hemianopia (confrontation testing)

Fundoscopy

• Optic disc pallor (if chronic compression)

With Dopamine Agonists

• 80-90% achieve normalised prolactin
• Tumour shrinkage in most

Long-Term

• Some can discontinue treatment after years (especially microprolactinomas)
• Recurrence possible after stopping treatment

Key Guidelines

1. Endocrine Society: Diagnosis and Treatment of Hyperprolactinemia (2011)
2. Pituitary Society Guidelines

Key Evidence

Cabergoline vs Bromocriptine

• Cabergoline more effective and better tolerated

What is a Prolactinoma?

A prolactinoma is a small, non-cancerous growth (tumour) on the pituitary gland at the base of the brain. It makes too much of a hormone called prolactin.

What Are the Symptoms?

Women:

• No periods or irregular periods
• Milky discharge from the nipples
• Difficulty getting pregnant

Men:

• Difficulty with erections
• Low sex drive
• Rarely, breast enlargement

Large tumours:

• Headaches
• Vision problems (especially peripheral vision)

How is It Treated?

• Tablets (dopamine agonists) are the main treatment and usually shrink the tumour and lower prolactin
• Surgery is rarely needed

What's the Outlook?

Most people respond very well to treatment. Some can eventually stop medication.