Prolactinoma

Meet the patient

A 28-year-old woman reaches the fertility clinic with eight months of secondary amenorrhoea, bilateral milky nipple discharge, and no conception after a year off contraception. She takes no psychotropic drug. The first move is not the pituitary MRI — it is a beta-hCG, because pregnancy is the commonest cause of amenorrhoea with galactorrhoea and you must not image a pregnant sella with gadolinium.[1]

The beta-hCG is negative. Her fasting serum prolactin is 4800 mU/L (about 240 ng/mL) — a level essentially diagnostic of a macroprolactinoma, because in a true prolactinoma the prolactin parallels tumour size. Two exam questions are now live, and everything below answers them: is the high prolactin a true tumour or a mimic? and why does this tumour get a tablet before an operation?[2]

The man across the bay tells the same story in reverse: a 45-year-old who has blamed his lost libido and erectile dysfunction on stress for three years, now brought in after he started bumping into door frames. His prolactin is over 10000 mU/L and his MRI shows a 3 cm macroadenoma kissing the chiasm. Men present late; the disease is identical, the delay is cultural.[8]

The one pituitary tumour a tablet fixes — the prolactinoma mantra

Cabergoline first, surgery selective. Prolactinoma is the single pituitary tumour in which a dopamine agonist is first-line and surgery is the exception, not the rule. The lactotroph is the only anterior pituitary cell under tonic inhibitory control, so restoring the dopamine brake with a D2 agonist does what a scalpel cannot always do safely: it normalises prolactin, shrinks the tumour in 60 to 90 percent of macroprolactinomas, relieves chiasmal compression within weeks, and switches ovulation back on.[2]

Contrast it with every other sellar mass and the teaching point writes itself: acromegaly, Cushing’s disease and the non-functioning macroadenoma all go to the transsphenoidal surgeon first. The prolactinoma goes to the pharmacist first. Hold that contrast and you hold the topic.[1]

The mantra, repeated until it is reflex: medical first, surgery selective — the one pituitary tumour a tablet fixes before a scalpel touches it. Every management decision on this page flows from that one line.[2]

How common, and the great sex gap nobody forgets twice

Prolactinoma is the commonest functioning pituitary adenoma — about 40 to 45 percent of them — and the sex ratio flips with tumour size. The clinically significant prevalence is around 6 to 10 per 100,000 with an annual incidence of 2 to 3 per 100,000; subclinical microadenomas lurk on roughly a tenth of unselected MRIs and almost never declare themselves.[1][2]

The face-off that earns marks is the sex gap. Microprolactinomas show a roughly 10 to 1 female predominance because amenorrhoea, galactorrhoea and infertility bring young women straight to the clinic. Macroprolactinomas sit near 1 to 1, because the male phenotype — slow loss of libido and erections — is blamed on age, stress or depression for years, so men arrive late with a chiasm-compressing mass.[2][8]

The discriminator beneath: it is not the tumour biology that differs by sex, it is the signal. Women bleed, leak and cannot conceive, so they present at 28; men go quiet and impotent, so they present at 48 with a field defect. Catch this once on a ward round and you never miss it again.[8]

[1] [2]

Four axes, four meanings — how to classify a prolactinoma

Classify along four axes: size, aggressiveness, prolactin species, and family. Each axis changes what you do, which is why a bare "prolactinoma" label is never enough for the viva.[1]

Size is the clinically dominant axis. A microprolactinoma is under 10 mm and is the common form in reproductive-age women; a macroprolactinoma is 10 mm or more, raises prolactin higher, threatens the chiasm, and dominates in men. Giant tumours (over 40 mm, or prolactin over 1000 ng/mL) invade the cavernous or sphenoid sinus and behave aggressively.[1][2]

Aggressiveness and prolactin species are the axes that bite. Most prolactinomas are slow-growing and dopamine-responsive; a minority invade and resist, demanding dose escalation, surgery, radiotherapy and — for the rare pituitary carcinoma — temozolomide. On the species axis, the assay measures monomeric, biologically active prolactin and also macroprolactin, a bio-inactive prolactin–IgG complex that reads high but does nothing — excluded by PEG precipitation before you image or treat anything.[1][5]

Family is the axis examiners probe in the young patient. Most are sporadic, but a prolactinoma in a young person, or with a family history of endocrine tumours, raises MEN1, MEN4, familial isolated pituitary adenoma (germline AIP — often macroadenomas in young men), Carney complex and rarely McCune-Albright.[2]

[1] [2] [5]

Read the prolactin like the lab does — the four thresholds

The prolactin level is one number with four interpretive bands, and the level must parallel the tumour. A single fasting, rested, morning sample — repeated if the rise is mild — is the single best test in the disease.[1]

[1]

The number rule for the viva: under 1000 think mimics, 1000 to 4000 think hard, over 4000 think macroprolactinoma, and always ask whether the number fits the tumour. A 3 cm mass is expected to sit on many thousands of mU/L; a 3 cm mass with a prolactin of 1500 is not a prolactinoma — it is a stalk effect, and operating on it as if it were is a serious surgical error.[1]

The three traps that wreck the diagnosis

Three named traps separate the competent prolactinoma answer from the dangerous one: the stalk effect, macroprolactin, and the high-dose hook effect. Each looks like a prolactinoma and none is treated like one.[1]

The classic trap — the stalk effect. Any large non-functioning sellar mass (non-functioning macroadenoma, craniopharyngioma, Rathke cyst, metastasis) compresses the stalk and cuts off tonic dopamine delivery to normal lactotrophs. They over-secrete, but only mildly — typically under 2000 mU/L, almost always under 4000. The discriminator: big tumour, small prolactin = stalk effect, not a prolactinoma. You treat the mass with surgery; a dopamine agonist will lower the prolactin but will not shrink a non-functioning tumour, so the mass effect worsens while the number looks better.[1]

Everyone forgets — macroprolactin. A prolactin–IgG complex reads high on the immunometric assay but is biologically inert, so the patient has a high prolactin with normal menses, no galactorrhoea and no tumour. Exclude it with polyethylene glycol (PEG) precipitation — a low post-PEG monomeric recovery (under 40 percent) closes the case — before you scan or treat anyone. Macroprolactin may coexist with a true prolactinoma, so do not dismiss a symptomatic patient on the strength of a macroprolactin result alone.[1]

The rare but catastrophic trap — the high-dose hook effect. In a giant macroprolactinoma with an enormous prolactin, antigen excess overwhelms the sandwich assay and reports a falsely low number. The clue is a tumour that looks far too big for its prolactin. The fix is to repeat the assay on a diluted sample (1 to 100 or 1 to 1000), which restores the antibody-to-antigen ratio and unmasks the true level. Miss it and you operate on a macroprolactinoma as a non-functioning mass.[1]

Etymology for viva gold: prolactin is from Latin pro, "for", and lac or lactis, "milk" — literally the milk-promoting hormone, named for the one thing it was first caught doing. Galactorrhoea rides the same root: Greek gala, "milk", plus rhoia, "flow". Both words outlived their metaphors because the physiology they name is unchanged.[1]

Why a tablet does what surgery cannot — the mechanism

The lactotroph is the only anterior pituitary cell under tonic inhibition, and the tumour escapes the brake — so you can put the brake back with a pill. The hypothalamus holds lactotrophs in check via dopamine from tuberoinfundibular neurons acting at the D2 receptor; cut the stalk and prolactin rises. Prolactin is unique among anterior pituitary hormones in being predominantly inhibited, not stimulated, by the hypothalamus.[1][2]

Once prolactin is over-produced it does three things, and the clinical picture is just those three things drawn out. First, it suppresses pulsatile GnRH, dropping FSH and LH and producing hypogonadotropic hypogonadism — amenorrhoea, anovulation, infertility, low libido, erectile dysfunction, and over the years osteoporosis. Second, it acts directly on breast epithelium to make milk, so galactorrhoea appears (its absence does not exclude the diagnosis, and men rarely get it for lack of an oestrogen-primed ductal tree). Third, the tumour itself compresses — chiasm first (bitemporal hemianopia, superior quadrants earliest), then the normal gland (gonadotrophs, then thyrotrophs, then corticotrophs, then somatotrophs), then the cavernous sinus (cranial nerves III, IV, V1, V2, VI).[1][7]

Consultant confession. Prolactin does not directly enlarge breast tissue in men; gynaecomastia is mild and indirect, driven by the relative oestrogen excess once testosterone is suppressed. Patients (and juniors) assume galactorrhoea equals high prolactin equals big tumour; the truth is that galactorrhoea needs an oestrogen-primed breast, so the symptom and the tumour size are only loosely linked.[8]

Two faces of one disease — woman early, man late

The face of prolactinoma is a reproductive and galactorrhoeic syndrome in women, and a slowly stolen sex life with late visual loss in men. The contrast is the single most under-recognised feature of the disease.[1][8]

The woman. The classic triad is galactorrhoea with oligomenorrhoea or amenorrhoea and infertility; add reduced libido, vaginal dryness and dyspareunia from oestrogen deficiency, and a fragility fracture from silent osteoporosis in long-standing disease. Many arrive through subfertility services, where a prolactin is part of the panel — which is exactly why small tumours are caught early here.[1]

The man. Progressive loss of libido, erectile dysfunction and oligospermic infertility are blamed on ageing, stress or depression for years before anyone measures a prolactin; gynaecomastia is modest and galactorrhoea is rare. By the time he presents, the tumour is a macroprolactinoma with headache, bitemporal field loss, cranial nerve palsies and partial hypopituitarism — the visual field defect is often the symptom that finally brings him in.[8]

Mass effect and apoplexy, either sex. Headache from diaphragma sellae stretch, bitemporal hemianopia from chiasmal compression, cranial nerve palsies from cavernous sinus invasion, CSF rhinorrhoea if the floor erodes into the sphenoid sinus with its meningitis risk, and anterior pituitary failure. Pituitary apoplexy — sudden severe headache, vomiting, visual loss, ophthalmoplegia, possible altered consciousness — is the emergency and lives in its own section below.[1]

The differential is a checklist, not a brainstorm

A raised prolactin has six categories, and you work them in order — physiological, drug, systemic, macroprolactin, stalk, tumour — before you commit anyone to a scan or a tablet. The Endocrine Society guideline codifies this exclusion, and examiners expect the order.[1]

Physiological first. Always a beta-hCG before anything else in a woman of reproductive age; then remember stress, sleep (prolactin peaks pre-dawn, hence a fasting resting morning sample), strenuous exercise, sexual intercourse and nipple stimulation. A single mildly raised sample is repeated fasting and rested before it is called pathological.[1]

Drugs are the great mimic. Anything that depletes dopamine or blocks D2 raises prolactin, usually under 2000 mU/L: risperidone is the worst antipsychotic, with haloperidol and phenothiazines behind it (clozapine, quetiapine and aripiprazole are largely spared); metoclopramide, domperidone and prochlorperazine; SSRIs and TCAs; opioids; verapamil, methyldopa and reserpine; omeprazole, cimetidine, ranitidine; high-dose oestrogens. Confirm by withdrawal and re-test when it is safe; if the antipsychotic cannot be stopped, liaise with psychiatry.[1]

Systemic, macroprolactin and stalk round out the list. Primary hypothyroidism raises TRH, which stimulates lactotrophs, and is fixed by levothyroxine; chronic kidney disease and cirrhosis reduce clearance; chest-wall lesions — zoster, thoracotomy, mastectomy, burns, chronic nipple stimulation — drive the suckling reflex; PCOS and infiltrative disease (sarcoid, histiocytosis, lymphocytic hypophysitis) complete the systemic tier. Macroprolactin is excluded by PEG; the stalk effect is a non-functioning mass compressing the stalk.[1]

[1]

The one-line discriminator beneath the table: prolactin that parallels tumour size is a prolactinoma; prolactin that does not is a stalk effect; prolactin that is high with no symptoms and no tumour is macroprolactin.[1]

[1]

The bedside round — fields, breasts, cranial nerves

Examination rarely makes the diagnosis; it detects mass effect, hypopituitarism and the bone consequences of chronic disease. Run it in three moves.[1]

History first. Map the menstrual pattern, the galactorrhoea (spontaneous versus expressible, bilateral versus unilateral, milky versus bloody — bloody is breast pathology, not prolactin), fertility, libido, headache and any visual symptom (bumping into objects, indistinct periphery), then a meticulous drug, thyroid, renal and hepatic history, chest-wall lesions, and a family history of endocrine tumours.[1]

Examination. Compress all four breast quadrants for expressible milky discharge; feel for true glandular gynaecomastia against fatty pseudogynaecomastia. Confront the visual fields finger-by-finger in each quadrant — any defect mandates urgent MRI and formal perimetry. Examine cranial nerves III, IV, V1, V2 and VI for cavernous sinus involvement, and look for hypothyroid, hypoadrenal (postural drop, pigmentation), hypogonadal (testicular atrophy, lost secondary hair) and osteoporotic (kyphosis, height loss) signs.[1][7]

Bone density is part of the workup, not an afterthought. A DEXA is baseline in long-standing disease, because hypogonadal osteoporosis is common, silent, and only partially reversible once established — the fracture risk outlasts the cure.[7]

Confirm, exclude, localise, assess — the investigation quartet

Investigation is a four-step algorithm: confirm genuine persistent hyperprolactinaemia, exclude the mimics, image the sella, and test the other axes plus mass effect. The order is examinable.[1]

Step 1 — confirm. A fasting, rested, morning serum prolactin, repeated if the rise is mild, confirms true hyperprolactinaemia. Apply the four thresholds: under 1000 mU/L (about 50 ng/mL) usually a mimic; 1000 to 4000 (about 50 to 200) indeterminate; over 4000 (about 200) essentially diagnostic of a macroprolactinoma; over 9400 (about 470) diagnostic. The level must parallel tumour size.[1]

Step 2 — exclude the mimics. Beta-hCG first; then TSH and free T4, urea and electrolytes and creatinine, LFTs, a careful drug history, and a macroprolactin screen by PEG precipitation (a post-PEG monomeric recovery under 40 percent closes it). Exclude macroprolactin before any tumour is sought or treated.[1]

Step 3 — localise and size. Pituitary MRI with gadolinium is the gold standard: it measures the greatest diameter, defines chiasmal contact, grades cavernous sinus invasion by the Knosp grade (0 to 4; grade 3 to 4 means invasion and predicts incomplete surgical resection), and looks for sphenoid extension. A microadenoma under 10 mm with a fitting prolactin confirms a microprolactinoma; a macroadenoma with prolactin over 4000 mU/L confirms a macroprolactinoma.[1]

Step 4 — assess mass effect and the other axes. For any macroadenoma, Humphrey perimetry and a full anterior pituitary panel — 9 am cortisol (or short Synacthen test), free T4 and TSH, LH and FSH with oestradiol or testosterone, IGF-1 — plus a DEXA for bone density. Dynamic tests (TRH stimulation, metoclopramide challenge, nomifensine suppression) are historical and rarely needed now that prolactin plus MRI settles most cases.[1][7]

Apoplexy is the emergency — do not wait for a cortisol

Prolactinoma is overwhelmingly a chronic, elective condition; the one true emergency is pituitary apoplexy, and the first drug is hydrocortisone, not a scan. Humour is off here.[1]

Apoplexy is haemorrhagic infarction of a macroprolactinoma: sudden severe headache, vomiting, rapidly progressive visual loss, ophthalmoplegia (a cranial nerve III palsy), and in severe cases altered consciousness or meningism. The immediate threat to life is acute corticotroph destruction and adrenal crisis, so you give steroids before you confirm anything.[1]

The bundle, in order: intravenous hydrocortisone 100 to 200 mg stat then 50 to 100 mg every 6 to 8 hours; intravenous fluids and haemodynamic support; urgent pituitary MRI to confirm and define the haemorrhage; urgent transsphenoidal decompression if vision, ophthalmoplegia or consciousness is deteriorating, with conservative monitoring acceptable only in the clinically stable patient without a visual deficit; and endocrine plus ophthalmology review. Do not wait for a cortisol result before giving steroids.[1]

Two adjacent emergencies share the resuscitation mindset. Acute adrenal crisis from hypopituitarism (hypotension, hyponatraemia, hypoglycaemia, confusion) gets intravenous hydrocortisone, fluids and glucose before any prolactinoma-specific therapy. CSF rhinorrhoea from a tumour eroding the sphenoid floor needs urgent neurosurgical review for ascending meningitis — note that a dopamine agonist shrinks the tumour but may worsen the leak as it pulls away from the defect.[1]

Cabergoline first, surgery selective — the management ladder

Four modalities, one order: dopamine agonist first, transsphenoidal surgery selective, radiotherapy rare, temozolomide for the aggressive or malignant few. Layered onto cause-treatment, axis-replacement and lifelong surveillance.[1][2]

Dopamine agonist — first-line for micro and macro alike, mass effect included. Restoring the D2 brake normalises prolactin, shrinks the tumour in 60 to 90 percent of macroprolactinomas (often visible on MRI within 6 to 12 weeks), relieves visual field defects within weeks, restores gonadal function and fertility, and stops galactorrhoea. Even a macroprolactinoma with a complete bitemporal hemianopia is treated medically first, with visual fields monitored closely as the tumour shrinks off the chiasm.[1][2]

Cabergoline is the preferred agent; bromocriptine and quinagolide are the alternatives. Cabergoline wins on efficacy, tolerability and twice-weekly dosing; bromocriptine carries the largest pregnancy-safety database and is preferred in some centres seeking conception, particularly in the first trimester; quinagolide is a non-ergot option in some markets. Start low at night with food, titrate by prolactin every 2 to 4 weeks, and warn every sexually active woman that ovulation can return within weeks — advise contraception if pregnancy is not desired.[1]

Surgery is selective, not default — and the indications are the exam list. Endoscopic transsphenoidal surgery by an experienced pituitary surgeon is reserved for dopamine-agonist resistance or intolerance, pituitary apoplexy with visual compromise, CSF rhinorrhoea, optic chiasm compression unresponsive to drugs, pregnancy with an enlarging macroprolactinoma, atypical or cystic tumours that may not shrink, and patient choice after balanced counselling. Remission runs around 60 to 90 percent for microprolactinomas but only 30 to 50 percent for macroprolactinomas, especially with cavernous sinus invasion.[3]

The 2020 Zamanipoor meta-analysis reopened surgery as a viable first-line alternative in selected micro- and small macroprolactinomas, with comparable remission and lower relapse after withdrawal — but international practice stays medical first, surgery selective. Expert-hand complications include hypopituitarism, diabetes insipidus, CSF leak, meningitis and cranial nerve injury.[3]

Radiotherapy is third-line; temozolomide is for the aggressive and malignant. Stereotactic radiosurgery or fractionated radiotherapy is reserved for refractory or residual disease after medical and surgical treatment; its drawbacks are a slow biochemical effect (months to years) and hypopituitarism as the commonest late complication, mandating lifelong axis surveillance. Temozolomide — 150 to 200 mg per square metre daily for 5 days of every 28-day cycle, over 3 to 6 cycles, with MGMT promoter methylation predicting response — is the specialist decision for the rare aggressive, resistant or frankly malignant pituitary carcinoma.[1][5]

Treat the cause and replace deficient axes. Withdraw offending drugs where safe; replace levothyroxine for hypothyroidism; replace cortisol (hydrocortisone 15 to 25 mg daily in divided doses, or prednisolone 3 to 5 mg) for ACTH deficiency — always before thyroid replacement, to avoid precipitating adrenal crisis; and give oestrogen or testosterone if gonadal function does not recover on a dopamine agonist. In microprolactinomas normalised and shrunken after 2 to 5 years, a supervised withdrawal keeps roughly 30 to 40 percent in remission; macroprolactinomas almost always relapse and need lifelong therapy.[1][6]

The surveillance clock

Surveillance is structured and lifelong for macroadenomas: prolactin every few months, MRI annually until stable, visual fields for any chiasmal contact, annual axes, and a DEXA at baseline. The timeline below is the schedule examiners ask for.[1][6]

When the disease bites back — complications and the preventable list

Harm comes from the disease (chronic hypogonadism, mass effect, apoplexy) and from its treatment (dopamine-agonist adverse effects, surgical and radiotherapy complications), and much of it is preventable with early, correct treatment.[1][7]

The disease harms bone, heart and sex — silently. Persistent hypogonadotropic hypogonadism drives osteoporosis and fragility fractures (often silent until a fracture, only partially reversible), dyslipidaemia and raised cardiovascular risk, loss of libido and erectile dysfunction, infertility, and psychological distress from galactorrhoea and altered body image. Mass effect adds bitemporal hemianopia (which can become permanent), cranial nerve palsies, hypopituitarism, CSF rhinorrhoea and apoplexy.[1][7]

The dopamine agonist has a named adverse-effect cluster you must ask about directly. Common and dose-related: nausea, postural hypotension, nasal congestion, headache, dizziness, fatigue. The ones juniors miss: impulse control disorder — pathological gambling, hypersexuality, compulsive shopping, especially with cabergoline — so ask directly at every review; CSF rhinorrhoea as a shrinking macroprolactinoma pulls away from a sphenoid floor defect; and, at high cumulative doses (as in Parkinson’s disease), cardiac valve regurgitation and retroperitoneal or pleural fibrosis — much less of a concern at standard prolactinoma doses, but a baseline echocardiogram is recommended for long-term use.[1][4]

[1] [4]

The cabergoline side-effect cluster, lettered for the viva — ask about impulse control at every review.[4]

[4]

The preventable-harm list — how prolactinoma patients come to grief.[1]

• Operating on a macroprolactinoma as a non-functioning mass because the stalk effect or hook effect was missed — the preventable operation.[1]
• Treating a stalk-effect mass with a dopamine agonist — the prolactin falls, the tumour does not, the mass effect worsens.[1]
• Imaging and treating macroprolactinaemia — high assay, no symptoms, no tumour, excluded by PEG.[1]
• Missing pregnancy — no beta-hCG first — and exposing a pregnant sella to gadolinium.[1]
• Forgetting a drug cause — risperidone, metoclopramide, verapamil, methyldopa.[1]
• Missing primary hypothyroidism — a TSH would have fixed it with levothyroxine.[1]
• Leaving chronic hypogonadism untreated until a fragility fracture declares the osteoporosis.[7]
• Giving thyroid replacement before cortisol and precipitating adrenal crisis.[1]
• Stopping cabergoline at a year in a macroprolactinoma because the patient felt well, with regrowth the result.[6]
• Not asking about gambling — an irreversible family and financial harm from a treatable drug side effect.[4]

Pregnancy, men, adolescents — the special populations

Special populations change presentation, thresholds and the balance of drug versus watchful waiting — they are NEET-PG and INICET staples.[1]

Pregnancy — the central scenario, decided by tumour size. Oestrogen-driven lactotroph hyperplasia means any prolactinoma may enlarge, and the risk is size-dependent. For a microprolactinoma the symptomatic-enlargement risk is under 5 percent: stop the dopamine agonist once pregnant, monitor clinically, image only if symptoms develop. For a macroprolactinoma the risk is over 20 percent: either continue bromocriptine or cabergoline through pregnancy with visual fields each trimester, or stop and monitor closely with re-introduction at the first symptom or field defect.[1]

Fertility restoration — the warning that earns marks. Cabergoline switches ovulation back on within weeks, so warn every sexually active woman that fertility may return before her first period, and advise contraception if pregnancy is not desired. Mechanical barrier contraception is preferred over the combined oral contraceptive, which can raise prolactin and obscure the return of menses as a marker of control.[1]

Men — the late presenters. Cabergoline normalises prolactin, raises testosterone, restores libido and erectile function, and improves fertility; testosterone replacement is reserved for persistent hypogonadism after prolactin normalises, because primary gonadal recovery is the rule if the mass effect is relieved in time. Persistent hypogonadism despite a normal prolactin raises a co-existent primary testicular disorder or irreversible gonadotroph damage from long-standing compression — check the bone density and treat the osteoporosis.[8]

Adolescents, the elderly, and organ failure. A prolactinoma in an adolescent — especially a macroadenoma in a young man — raises a germline AIP mutation (familial isolated pituitary adenoma) and warrants genetic testing; cabergoline stays first-line, surgery for resistance or apoplexy. The elderly present with visual loss, headache or hypopituitarism from a long-standing macroprolactinoma, with galactorrhoea and menstrual features absent or attributed to ageing; comorbid valve disease and postural hypotension shape drug choice. In hepatic or renal impairment, dose-caution the agonist, remember that renal disease itself raises prolactin by reduced clearance, and note that domperidone and metoclopramide are commoner drug culprits there.[1][2]

Where the guideline stands, and where it is shaky

The 2011 Endocrine Society guideline (Melmed and colleagues) is the practice-defining document; the debates around it are exactly what examiners probe.[1]

The guideline codified the diagnostic exclusion of pregnancy, drugs, hypothyroidism, renal failure and macroprolactin; made dopamine agonists — cabergoline first — the cornerstone; set the essentially-diagnostic prolactin threshold; and laid out the pregnancy algorithm by tumour size. The Gillam 2006 Endocrine Reviews review underpins much of the cabergoline-versus-bromocriptine efficacy and tolerability evidence.[1][2]

Where the evidence is weak — name these calmly. The exact "essentially diagnostic" threshold (200 versus 250 ng/mL) is consensus-dependent; the place of routine surgery in microprolactinoma is debated (Zamanipoor makes a strong case, but practice stays medical); the timing and necessity of echocardiographic screening at standard cabergoline doses is unresolved; the role of temozolomide in non-malignant aggressive prolactinoma is still being defined; and the optimal duration of therapy before a withdrawal attempt is individualised rather than protocolised.[3][6]

Six pearls that decide a prolactinoma answer — carry these into the viva.[1]

Ward-round test

Stem 1. A 26-year-old woman has secondary amenorrhoea, bilateral galactorrhoea and a serum prolactin of 4200 mU/L (about 210 ng/mL). What is the very first test you order, and why?[1]

Reveal

A beta-hCG — pregnancy is the commonest cause of amenorrhoea with galactorrhoea and must be excluded before any imaging or dopamine agonist. Only then a fasting prolactin (already done here) and a pituitary MRI; a level over 4000 mU/L is essentially diagnostic of a macroprolactinoma and the prolactin should parallel tumour size.[1]

Stem 2. A 48-year-old man has a 4 cm pituitary mass, a bitemporal hemianopia and a prolactin of 1800 mU/L (about 90 ng/mL). Is this a prolactinoma, and what is the first-line treatment?[1]

Reveal

No — this is the stalk effect. Big tumour, small prolactin: in a true prolactinoma the prolactin parallels tumour size, so a 4 cm mass should sit on many thousands of mU/L. Treat the non-functioning mass with transsphenoidal surgery, not a dopamine agonist — a dopamine agonist will lower the prolactin but will not shrink the tumour.[1]

Stem 3. A 35-year-old man has a 3 cm macroprolactinoma and a reported prolactin of only 1500 mU/L. What single laboratory step do you take before believing the number?[1]

Reveal

Repeat the assay on a diluted sample (1 to 100 or 1 to 1000) to exclude the high-dose hook effect — antigen excess has overwhelmed the sandwich assay and reported a falsely low value. Missing this leads to the catastrophic error of operating on a macroprolactinoma as a non-functioning mass.[1]

Stem 4. A woman with a macroprolactinoma conceives on cabergoline. How does management differ from a microprolactinoma in pregnancy, and what is the one symptom she must report immediately?[1]

Reveal

For a microprolactinoma, stop the dopamine agonist once pregnant (symptomatic-enlargement risk under 5 percent); for a macroprolactinoma, continue the agonist and check visual fields each trimester (risk over 20 percent). She must report any new headache or visual change immediately — it signals symptomatic enlargement and mandates urgent MRI and fields.[1]

References

1. [1]Melmed S, Casanueva FF, Hoffman AR, Kleinberg DL, Montori VM, Schlechte JA, Wass JA. Diagnosis and treatment of hyperprolactinemia: an Endocrine Society clinical practice guideline J Clin Endocrinol Metab, 2011.PMID 21296991
2. [2]Gillam MP, Molitch ME, Lombardi G, Colao A. Advances in the treatment of prolactinomas Endocr Rev, 2006.PMID 16705142
3. [3]Zamanipoor Najafabadi AH, Zandbergen IM, de Vries F, Broersen LHA, van den Akker-van Marle ME, Pereira AM, et al. Surgery as a Viable Alternative First-Line Treatment for Prolactinoma Patients. A Systematic Review and Meta-Analysis J Clin Endocrinol Metab, 2020.PMID 31665485
4. [4]Valassi E, Klibanski A, Biller BM. Clinical Review#: Potential cardiac valve effects of dopamine agonists in hyperprolactinemia J Clin Endocrinol Metab, 2010.PMID 20130078
5. [5]Hagen C, Schroeder HD, Hansen S, Andersen M. Temozolomide treatment of a pituitary carcinoma and two pituitary macroadenomas resistant to conventional therapy Eur J Endocrinol, 2009.PMID 19654234
6. [6]Lee MH, Hong JW, Kim K, Ku CR. Elucidating Clinical Queries for Tailored Therapy in Patients with Prolactinoma Endocrinol Metab (Seoul), 2024.PMID 39397514
7. [7]Uygur MM, Menotti S, Santoro S, Giustina A. Modern approach to bone comorbidity in prolactinoma Pituitary, 2024.PMID 39541075
8. [8]Rudman Y, Shimon I. Hypogonadism in men with prolactinoma: Diagnosis, treatment, and management of persistent hypogonadism Vitam Horm, 2025.PMID 40812946