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MEN4 and CDKN1B: the rare relative of MEN1 | CION Cancer Clinics
MEN4 is a rare inherited condition caused by a fault in a gene called CDKN1B. It looks a lot like MEN1, with overactive parathyroid glands and pituitary tumours, but it tends to be milder and appear later. It is usually found when someone has MEN1-type tumours and the MEN1 test comes back clear. This page explains what CDKN1B does, what MEN4 involves, and how much is still unknown. At CION Cancer Clinics, our oncologists explain what a gene result means for you and your family, and plan the checks that follow.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
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On this page
- What is MEN4, and how is it different from MEN1?
- Which glands does MEN4 affect?
- How does a family end up with a MEN4 diagnosis?
- The words you will meet, in plain language
- MEN1 and MEN4, compared
- Four things families tell us, and what is actually true
- What this page cannot tell you
- Common questions about MEN4 and CDKN1B
The short answer
What is MEN4, and how is it different from MEN1?
MEN4 is a rare inherited condition caused by a fault in a gene called CDKN1B. It looks like MEN1, with overactive parathyroid glands and pituitary tumours, but it is far less common and seems to be milder and later in onset. It is usually found when someone has MEN1-type tumours and the MEN1 test comes back clear.
How it was found
Researchers first noticed a similar condition in a strain of laboratory rats. The same gene was then found to be faulty in a family with pituitary and parathyroid tumours. Since then, only a few dozen families have been described in medical journals worldwide. That is why so much about MEN4 is still uncertain.
Why it has its own name
Knowing the exact gene matters for relatives. If a family's tumours are caused by CDKN1B, relatives can be tested for that fault. Those who do not carry it can stop screening. Without the right gene, everyone would have to be watched on the family history alone.
MEN4 is rare. Most people with MEN1-type tumours and a clear MEN1 test do not have it.What it affects
Which glands does MEN4 affect?
The pattern overlaps with MEN1, but the balance between glands is different, and the numbers are small.
Parathyroid glands
The most commonly reported problem. The calcium in the blood rises because a parathyroid gland is overactive. In MEN4 it more often affects a single gland and tends to appear later than in MEN1.
Pituitary gland
The second most common problem. Several types have been reported, including tumours that make growth hormone or prolactin, and some that make no hormone at all.
Can cause
- Enlarging hands, feet or jaw
- Changes to periods or breast milk
- Headaches or changes in vision
Pancreas and gut
Neuroendocrine tumours of the pancreas, duodenum or stomach have been reported, but less often than in MEN1. These are the tumours with the most potential to spread.
Other reported tumours
Single families have had adrenal, kidney, thyroid, lung or womb tumours. With so few cases, it is not clear which of these are truly linked and which are coincidence.
Not sure whether this applies to you?
Ask an oncologistHow it is usually found
How does a family end up with a MEN4 diagnosis?
-
A MEN1-type tumour appears
Someone develops an overactive parathyroid gland, a pituitary tumour or both, often at a younger age than expected, or with relatives who had similar problems.
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The MEN1 test comes back clear
MEN1 is the usual first suspect. When no fault is found, the doctor looks wider, because the tumours still suggest something inherited.
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A wider panel includes CDKN1B
Many laboratories now test CDKN1B on the same endocrine panel as MEN1, so it may be checked at the same time from the start.
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The change is classified
Many CDKN1B changes found so far are labelled uncertain. Only a change classed as disease-causing leads to screening and family testing.
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Relatives are offered testing
Once a clear fault is confirmed, parents, brothers, sisters and children can be tested for it directly.
On your report
The words you will meet, in plain language
- CDKN1B
- The gene behind MEN4. It makes a protein that acts as a brake on cell division.
- p27
- The name of the protein CDKN1B makes. When there is too little of it, cells in some glands divide more than they should.
- Tumour suppressor gene
- A gene whose normal job is to hold back growth. MEN1 and CDKN1B are both of this kind.
- Phenocopy
- Someone who has MEN1-type tumours but no inherited fault. Their tumours arose by chance, not from a family gene.
- Variant of uncertain significance
- A change the laboratory cannot yet classify. It should not change your care or lead to testing of relatives.
- Penetrance
- How often a fault actually leads to a tumour across everyone who carries it. For MEN4 this has not been measured well.
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Side by side
MEN1 and MEN4, compared
MEN1
MEN4
Caused by a fault in MEN1
Caused by a fault in CDKN1B
Rare, but well studied
Much rarer, with few families described
Parathyroid disease usually in several glands
Parathyroid disease more often in one gland
Almost every carrier affected by middle age
How many carriers are affected is not known
Written international screening guidance
Screening borrowed from MEN1 and adjusted
Commonly believed
Four things families tell us, and what is actually true
"My MEN1 test was clear, so nothing is inherited."
A clear MEN1 test rules out one gene. If your tumours and family history still look inherited, other genes such as CDKN1B may be worth checking. Ask whether your panel included them.
"MEN4 is just a milder MEN1, so it can be ignored."
It may be milder on average, but tumours of the pancreas and gut have been reported. Carriers still need a checking plan, even if it is lighter than for MEN1.
"Any change in CDKN1B means we have MEN4."
Many changes in this gene are harmless or uncertain. Only a change classed as disease-causing confirms MEN4. An uncertain result should not change your care.
"If my parent has no tumour, I cannot carry it."
Not every carrier develops a tumour, and some develop one late in life. A parent may carry the fault without knowing. Only a test settles who carries it.
Being straight with you
What this page cannot tell you
It cannot tell you how likely you are to develop a tumour. With so few families described, nobody knows the lifetime risk for a MEN4 carrier. What your specific variant means is a question for the counsellor who ordered the test.
The evidence is genuinely thin
There is no screening guideline written for MEN4 alone. Most specialists use the MEN1 schedule as a starting point and lighten it, focusing on calcium and pituitary checks. That is a reasonable approach, but it is expert opinion rather than proven practice. Plans may change as more families are studied.
Who this does not apply to
Most people with a single parathyroid problem in later life have no inherited fault at all. This page is also not about a CDKN1B change found only in tumour tissue, which is covered on our targeted therapy pages and is not passed on to children.
If your report mentions CDKN1B, ask your counsellor exactly how the change is classified before acting on it.Questions we are asked
Common questions about MEN4 and CDKN1B
How rare is MEN4?
Very rare. Only a few dozen families have been reported worldwide, and it explains only a small share of people who have MEN1-type tumours with a clear MEN1 test. Most such people have no inherited fault found at all.
Is MEN4 inherited the same way as MEN1?
Yes. One faulty copy from either parent is enough. Each child of a carrier has a one in two chance of inheriting it. Not every carrier develops a tumour, which can make the pattern hard to see in a family.
What checks does a MEN4 carrier need?
There is no fixed guideline. Most specialists suggest regular blood tests for calcium and pituitary hormones, with scans of the pituitary and belly at intervals. Your endocrinologist will set a plan based on your family's tumours.
Should my children be tested?
This depends on the tumours seen in your family. Childhood tumours have not been a clear feature of MEN4 so far, so testing can often wait. Your counsellor will advise on timing for your family.
Can I have both MEN1 and MEN4?
This would be extremely unusual. In practice, a family's tumours are explained by one gene or the other. A panel that tests both at once avoids repeat testing and saves time.
Are there other genes like CDKN1B?
Yes. Faults in a few related brake genes have been reported in single families with MEN1-type tumours. Pituitary tumours alone can also be linked to other genes. Your counsellor will explain which ones your panel covered.
My result says uncertain. What now?
Carry on with care based on your own tumours and family history. An uncertain change should not lead to extra scans or family testing. Ask how you will be told if the laboratory reclassifies it later.
Where can I be tested in Hyderabad?
Several laboratories in Hyderabad offer endocrine panels that include CDKN1B. Arranging it through a genetic counsellor makes sure the right panel is chosen. Call the CION helpline and someone will guide you to the right clinic.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
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Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
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Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
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Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
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Sources
- MedlinePlus Genetics — CDKN1B gene
- MedlinePlus Genetics — Multiple endocrine neoplasia
- GeneReviews (NCBI) — Multiple Endocrine Neoplasia Type 1
- National Cancer Institute — Genetic Testing for Inherited Cancer Susceptibility Syndromes
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
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