Health condition
MEN1, the parathyroid, pancreatic and pituitary triad - explained.
An inherited condition that raises the risk of tumours in three glands. Genetic testing and lifelong surveillance catch problems early, when they are most treatable.
Why trust this guide
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Editorial team
Written by our editorial team from the UK sources listed on each page.
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Sourced from guidance
Checked against Endocrine Society and UK MEN1 consensus guidance you can see at the end.
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Current for 2026
Reflects modern genetic testing, lifelong surveillance and specialist MDT pathways for MEN1.
Key facts
MEN1 at a glance.
The essentials, in plain English - what it is, how it's inherited, and how it's monitored in the UK today.
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What it is
An inherited tumour predisposition syndrome caused by a mutation in the MEN1 gene, which normally makes the tumour-suppressor protein menin.
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Inheritance
Autosomal dominant - each child of an affected parent has a 50% chance of inheriting the mutation.
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The classic triad
Known as the "3 Ps" - parathyroid, pancreatic/duodenal and pituitary tumours, though not everyone develops all three.
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Most common sign
Primary hyperparathyroidism, affecting around 95% of carriers and often the first thing that is noticed.
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Why it matters
Tumours can appear from childhood onward and some pancreatic lesions carry malignant potential, so lifelong screening is central.
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Genetic testing
MEN1 gene sequencing confirms the diagnosis and allows cascade testing of at-risk relatives.
Why this guide matters
Early recognition changes the whole course.
MEN1 is rare, lifelong and manageable - with the right genetic testing and surveillance in place. The three points below shape everything else on this page.
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One gene, three glands
A single MEN1 mutation raises the risk of tumours in the parathyroid, pancreas/duodenum and pituitary - rarely all at once, but often over a lifetime.
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Genetics unlocks the family
Confirming the mutation in one person allows cascade testing that identifies at-risk relatives years before symptoms would appear.
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Surveillance beats symptoms
Annual bloods and periodic imaging catch tumours - including those with malignant potential - while they are still small and manageable.
How the diagnosis is made
From clinical suspicion to a lifelong plan.
The steps a UK specialist genetics and endocrinology team will normally follow, in order - so you know what to expect and why.
Phase 1 · Assessing
Clinical suspicion and baseline bloods
Phase 2 · Confirming
Genetic testing and family screening
Phase 3 · Preparing
Imaging and lifelong surveillance
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Assessing
Clinical suspicion
Two or more of the classic MEN1 tumours in one person, or one such tumour plus a family history, prompts assessment.
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Assessing
Baseline biochemical screening
Calcium and PTH, fasting gut hormones and gastrin, prolactin and IGF-1 - the first-line blood tests for each arm of the triad.
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Assessing
Genetic counselling
A specialist genetics discussion before testing, covering implications for the person and their relatives.
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Confirming
MEN1 gene sequencing
Specialist commissioned clinical genetics testing confirms the mutation and its exact type.
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Confirming
Cascade testing of relatives
First-degree relatives are offered testing for the family’s specific mutation once it is known.
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Preparing
Baseline imaging
MRI pituitary and pancreatic imaging (MRI or endoscopic ultrasound) map out any tumours already present.
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Preparing
Lifelong surveillance plan
Annual biochemistry and periodic imaging from childhood in confirmed carriers, coordinated by a specialist MEN clinic.
Typical timeline: genetic confirmation in weeks, then surveillance for life.
Symptoms
What MEN1 can look like.
Signs from any of the three glands, plus a few less common features. And the features that mean it's time to escalate.
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Parathyroid - hyperparathyroidism
Raised calcium, kidney stones, bone pain or fatigue from multigland parathyroid overactivity - the most common first sign.
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Gastrinoma (Zollinger-Ellison)
Recurrent or severe peptic ulcers and persistent diarrhoea from gastrin-secreting pancreatic or duodenal tumours.
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Insulinoma
Episodes of hypoglycaemia - sweating, confusion, tremor - relieved by eating, from insulin-secreting tumours.
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Prolactinoma
Irregular periods, reduced libido or milky nipple discharge in women; low libido or erectile difficulty in men.
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Growth hormone excess
Enlarging hands, feet or jaw, and other features of acromegaly, from a growth hormone-secreting pituitary adenoma.
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Adrenal tumours
Often found incidentally on imaging - usually non-functioning but occasionally hormone-secreting.
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Skin lesions
Facial angiofibromas, collagenomas and lipomas are common cutaneous clues, though rarely the reason people seek help.
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Red flag - non-functioning pancreatic NET
Pancreatic neuroendocrine tumours with no hormone symptoms still carry malignant potential and need active surveillance.
Treatment
How MEN1 is managed in the UK.
Gland-specific treatment for each tumour that develops, wrapped in lifelong surveillance and genetic support for the whole family.
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Parathyroidectomy
Subtotal or total parathyroidectomy with autotransplantation, rather than removing a single gland, because multigland disease is typical in MEN1.
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High-dose proton pump inhibitors
First-line acid control for gastrinoma and Zollinger-Ellison syndrome, often at higher doses than for ordinary reflux.
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Selective gastrinoma surgery
Resection considered case by case - gastrinomas are often multifocal in MEN1, so surgical cure is less certain than in sporadic disease.
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Somatostatin analogues
Used for metastatic gastrinoma or advanced pancreatic neuroendocrine tumours to control hormone secretion and slow growth.
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Insulinoma enucleation
Surgical enucleation or resection is the standard treatment once an insulinoma is localised.
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Dopamine agonists
First-line medical treatment for prolactinomas, usually shrinking the tumour and normalising prolactin.
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Pituitary surgery
Reserved for larger or non-prolactin-secreting pituitary tumours, or those resistant to medical treatment.
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Pancreatic NET resection
Surveillance for small non-functioning tumours, with surgery considered for larger or growing lesions given their malignant potential.
Lifelong surveillance
Annual biochemical screening and periodic pituitary and pancreatic imaging continue for life in confirmed carriers, coordinated by a specialist MEN clinic.
Genetic counselling and family testing
Specialist genetics teams support decisions about testing at-risk relatives and discuss the implications for planning a family.
Care is delivered by a specialist commissioned multidisciplinary team - endocrinology, endocrine surgery and clinical genetics - often alongside AMEND, the UK patient association for MEN disorders.
What this guide is based on
The sources behind every claim on this page.
Specialist society guidance and UK commissioning standards, current at the time of last review.
Key references
Guidelines and standards we relied on.
A quiet reminder
This guide is for information, not medical advice.
Your specialist endocrinology and genetics team knows your history and can tell you which parts apply to you. If in doubt, get seen.
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Endocrine Society. Clinical practice guideline: multiple endocrine neoplasia type 1.
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UK MEN1 consensus guidance for diagnosis, screening and management.
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AMEND (Association for Multiple Endocrine Neoplasia Disorders). Patient information and support.
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NHS specialist commissioning guidance for MEN syndromes and endocrine surgery.
Red flags
When MEN1 needs urgent attention.
Most MEN1 tumours are picked up on routine surveillance. These are the situations that aren't - and where urgent review is needed.
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Severe hypercalcaemia
Confusion, vomiting or marked dehydration alongside a high calcium level needs urgent assessment.
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Recurrent or bleeding peptic ulcers
Ulcers that keep coming back, bleed, or fail standard treatment should prompt gastrin testing for Zollinger-Ellison syndrome.
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Severe or unrecognised hypoglycaemia
Confusion, seizures or loss of consciousness from low blood sugar, especially fasting, needs same-day medical review.
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Rapidly growing pancreatic tumour
Any pancreatic neuroendocrine lesion that grows quickly or exceeds size thresholds on surveillance imaging warrants prompt specialist reassessment.
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Visual field loss or severe headache
Can signal a large pituitary tumour pressing on the optic chiasm - needs urgent imaging and endocrine or neurosurgical review.
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Adrenal mass with hormone symptoms
An adrenal tumour causing high blood pressure, unusual weight change or virilisation needs urgent endocrine assessment.
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New symptoms in a known carrier
Any new symptom in someone with a confirmed MEN1 mutation should be discussed with their specialist MEN team rather than waited out.
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Missed surveillance
Falling behind on annual bloods or imaging in a known carrier is itself a red flag - re-engage with the specialist clinic promptly.
Living with it
A lifelong condition, with a clear rhythm.
Four things that make the biggest difference over the years - staying on top of screening, attending imaging, involving the family and finding support.
A quiet reminder
Consistent surveillance beats reacting to symptoms.
A quiet routine of annual bloods and periodic scans, kept up for decades, is what actually protects you.
- 01 Screen
Keep annual bloods on track
Yearly calcium, PTH, gut hormones, gastrin, prolactin and IGF-1 catch new tumours early, often before symptoms appear.
- 02 Image
Attend periodic imaging
MRI pituitary and pancreatic imaging on the schedule your specialist team sets, even when you feel well.
- 03 Family
Talk to relatives about testing
Cascade genetic testing lets at-risk relatives start their own surveillance early, before problems develop.
- 04 Support
Connect with AMEND
The Association for Multiple Endocrine Neoplasia Disorders offers patient information, peer support and specialist clinic links.
Frequently asked
Everything we get asked about MEN1.
Quick answers on inheritance, the triad, genetic testing and surveillance.
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What is MEN1?
Multiple endocrine neoplasia type 1 is an inherited condition caused by a mutation in the MEN1 gene, which normally produces the tumour-suppressor protein menin. It predisposes carriers to tumours of the parathyroid, pancreas/duodenum and pituitary gland, along with several less common manifestations.
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Is MEN1 hereditary?
Yes. It is autosomal dominant, meaning a single altered copy of the gene is enough to cause the condition, and each child of a carrier has a 50% chance of inheriting it. Genetic counselling and cascade testing of relatives are a core part of management.
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What are the "3 Ps" of MEN1?
Parathyroid (primary hyperparathyroidism, the most common feature), Pancreatic/duodenal (gastrinomas, insulinomas and non-functioning neuroendocrine tumours), and Pituitary (most often prolactinomas, but also growth hormone or ACTH-secreting adenomas).
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Why is parathyroid surgery different in MEN1?
Because multigland disease is typical rather than a single overactive gland, surgeons usually perform a subtotal or total parathyroidectomy with autotransplantation instead of removing just one gland, to reduce the chance of the condition recurring.
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How often is screening needed?
Guidelines recommend annual biochemical screening - calcium, PTH, fasting gut hormones, gastrin, prolactin and IGF-1 - from childhood in confirmed carriers, alongside periodic pituitary and pancreatic imaging, coordinated through a specialist MEN clinic.
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Can MEN1 tumours become cancerous?
Most MEN1 tumours are benign, but some pancreatic neuroendocrine tumours carry malignant potential, which is why surveillance and, when needed, surgical resection of larger or growing lesions are important parts of lifelong care.