Prolactinoma (hyperprolactinaemia) !
A benign pituitary tumour that makes too much prolactin. It stops periods, causes milk discharge and infertility, and usually shrinks with tablets.
Updated 2026-11-01
Structures involved
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In embryology
Why it happens
- Prolactin and its control by dopamine
- The hypothalamic–pituitary system: overview
- The menstrual cycle: ovary and endometrium
- Pituitary: adenohypophysis and neurohypophysis
What it is
A benign tumour of the lactotroph cells of the anterior pituitary that secretes excess prolactin. It is the most common hormone-secreting pituitary adenoma and the classic cause of pathological hyperprolactinaemia.
Who gets it
The most frequent functioning pituitary tumour worldwide and in Latin America. Microprolactinomas predominate in women of reproductive age; men tend to present later with larger tumours because early symptoms are less obvious.
Causes
- Monoclonal growth of prolactin-secreting lactotroph cells, usually sporadic
- Occasionally part of an inherited syndrome, most often multiple endocrine neoplasia type 1
- Other causes of high prolactin must be excluded: pregnancy, drugs that block dopamine, hypothyroidism, kidney failure and stalk compression
Risk factors
- Female sex, ages 20 to 50 for microadenomas
- Family history of MEN 1
- Oestrogen exposure may promote growth of an existing tumour (e.g. in pregnancy)
Pathophysiology
Prolactin is normally held in check by dopamine from the hypothalamus. Excess prolactin suppresses hypothalamic GnRH pulses, so LH, FSH and sex steroids fall, causing anovulation, amenorrhoea, low testosterone and bone loss. A large tumour can also compress the optic chiasm above the sella or the normal pituitary, causing visual loss and hypopituitarism.
Classification
- Microprolactinoma: under 10 mm
- Macroprolactinoma: 10 mm or more, may invade the cavernous sinus
- Giant prolactinoma: 40 mm or more
Symptoms and signs
- Women: oligomenorrhoea or amenorrhoea, galactorrhoea and infertility
- Men: low libido, erectile dysfunction, infertility and sometimes gynaecomastia
- Headache with larger tumours
- Visual field loss, classically bitemporal hemianopia, with macroadenomas
- Reduced bone density from long-standing low sex hormones
Diagnosis
- Clinical
- Menstrual and fertility history, galactorrhoea, sexual function, visual field testing by confrontation, and a careful drug history.
- Tests
- Serum prolactin (marked elevation supports a prolactinoma); pregnancy test, TSH and free T4, and creatinine to exclude other causes. In a large tumour with only mild elevation, a diluted sample excludes the hook effect. Other pituitary axes (morning cortisol, LH, FSH, sex steroids, IGF-1) are assessed in macroadenomas. Formal visual field perimetry.
- Imaging
- Pituitary MRI with gadolinium is the imaging study of choice; it sizes the tumour and shows extension to the chiasm or cavernous sinus.
Differential diagnosis
- Pregnancy and breastfeeding
- Drug-induced hyperprolactinaemia (antipsychotics, metoclopramide and other dopamine antagonists)
- Primary hypothyroidism
- Stalk effect from a non-functioning macroadenoma or craniopharyngioma
- Chronic kidney disease and macroprolactinaemia
Goal of treatment
Normalise prolactin, restore gonadal function and fertility, shrink the tumour and protect vision, while preserving the rest of pituitary function.
Treatment
- Medical
- Dopamine agonists (cabergoline, bromocriptine) are first-line even for macroadenomas with visual loss; they lower prolactin and shrink most tumours. Valvular heart disease is monitored when high cumulative doses are used.
- Surgical
- Transsphenoidal surgery for intolerance or resistance to dopamine agonists, apoplexy, or vision that does not improve.
- Procedure
- Radiotherapy is reserved for aggressive tumours not controlled by medicine and surgery.
- Follow-up
- Serial prolactin, repeat MRI and visual fields; closer follow-up in pregnancy because a macroadenoma can enlarge.
Drugs for this condition
Complications
- Infertility and amenorrhoea
- Osteoporosis from long-standing hypogonadism
- Visual loss from chiasmal compression
- Hypopituitarism and pituitary apoplexy
- CSF leak after rapid tumour shrinkage
Prognosis
Most microprolactinomas are controlled with medication and some never grow. Many patients can eventually taper treatment, but prolactin may rise again, so long-term follow-up is needed.
Test yourself
Think of the answer, then tap the question to see it.
What is the first-line treatment of a prolactinoma, even with visual field loss?
A dopamine agonist such as cabergoline or bromocriptine; surgery is reserved for intolerance, resistance or apoplexy.
Why does hyperprolactinaemia cause amenorrhoea and low testosterone?
Prolactin suppresses hypothalamic GnRH pulsatility, so LH and FSH fall and the gonads make less sex steroid.
Which visual field defect is classic for a pituitary macroadenoma?
Bitemporal hemianopia, from compression of the optic chiasm.
Which common conditions must be excluded before blaming a pituitary tumour for high prolactin?
Pregnancy, dopamine-blocking drugs (e.g. antipsychotics), primary hypothyroidism and kidney failure.
Related conditions
- Pituitary adenoma
- Hypopituitarism (incl. Sheehan syndrome and pituitary apoplexy)
- Male hypogonadism
- Multiple endocrine neoplasia (MEN 1, 2A, 2B)
- Hypothyroidism
- Osteoporosis
- Polycystic ovary syndrome
- Functional hypothalamic amenorrhoea
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Prolactinoma (MedlinePlus Medical Encyclopedia (U.S. National Library of Medicine), 2025).
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