Hematologist
CION Cancer Clinics
Your thyroid after radiotherapy to the neck | CION Cancer Clinics
Radiotherapy to the neck or upper chest for lymphoma often leads to an underactive thyroid, sometimes many years after treatment. A simple thyroid blood test once a year is usually advised for life, and an underactive thyroid is treated with a daily tablet. This page explains the signs, the yearly check, the words on your report and what to know if you are started on thyroid tablets. At CION Cancer Clinics, our haematology team plans myeloma and lymphoma care with you, discussed at a tumour board and explained in plain words.
BP
Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
17+specialists on panel
15,000+patients treated
35+centres across Telangana & AP
4.8★ / 800+Google rating
On this page
- Does radiation to the neck for lymphoma affect the thyroid?
- What does an underactive thyroid feel like?
- Which thyroid problems can follow neck radiation?
- How is the thyroid checked after treatment?
- What do the words on a thyroid report mean?
- What do survivors often believe about thyroid tablets?
- What should I know if I am put on thyroid tablets?
- Common questions about the thyroid after neck radiation
The short answer
Does radiation to the neck for lymphoma affect the thyroid?
Often, yes. Radiotherapy to the neck or upper chest for lymphoma commonly leads to an underactive thyroid, sometimes many years later, so a simple thyroid blood test every year is usually advised for life. An underactive thyroid is easy to test for and is treated with a daily tablet.
Why the thyroid is affected
The thyroid is a small gland at the front of the neck. It makes the hormone that sets how fast your body runs. When lymph nodes in the neck or chest are treated, the thyroid often lies inside or close to the radiation field. Over time the gland can slowly make less hormone.
It can happen long after treatment
The change is usually gradual. Some people have a normal test for years and then a slowly rising result. That is why a single normal result after treatment does not mean checks can stop.
Who this does not apply to
If your radiotherapy did not include the neck or upper chest, or you had chemotherapy alone, this particular risk is much lower. Your treatment summary shows which areas were treated.
Signs to mention
What does an underactive thyroid feel like?
The signs creep in slowly and are easy to blame on age, stress or past treatment. Many people have none at all.
- Tiredness that sleep does not fix
- Feeling cold when others are comfortable
- Weight gain without eating more
- Dry skin, thinning hair or brittle nails
- Hard stools and slow digestion
- Low mood, poor memory or slow thinking
- Heavier or irregular periods
- A puffy face or hoarse voice
Not sure whether this applies to you?
Ask an oncologistPossible effects
Which thyroid problems can follow neck radiation?
An underactive thyroid is by far the most common. The others are less common but are the reason the neck is also examined.
Underactive thyroid
The gland makes too little hormone. Doctors call it hypothyroidism. It may first show only on a blood test, before any symptoms.
Usually managed with
- A daily thyroid hormone tablet
- Repeat blood tests to adjust it
Overactive thyroid
Less often, the gland becomes inflamed or overactive for a time, causing a racing heart, weight loss, sweating or shakiness. It needs a doctor's assessment.
Thyroid lumps
Small lumps, called nodules, are more common after neck radiation. Most are harmless. An ultrasound scan is used to decide whether one needs a closer look.
Thyroid cancer, rarely
The risk of thyroid cancer is raised years after neck radiation, but it remains uncommon. A new or growing lump in the neck should be reported and examined.
The yearly check
How is the thyroid checked after treatment?
Know you need it
Check your treatment summary for radiation to the neck, chest or both. Tell your family doctor, so the test is not forgotten once haematology visits end.
A blood test once a year
A simple thyroid function test, usually TSH and sometimes free T4, from an ordinary blood sample. It can be done at a nearby laboratory in your district.
A look at your neck
Your doctor feels the neck for lumps at routine visits. If a lump is found, an ultrasound scan is usually the next step.
Results read over time
One result is compared with your earlier ones. Reference ranges differ between laboratories, and a borderline result is often repeated before any treatment starts.
On your report
What do the words on a thyroid report mean?
- TSH
- A hormone from the brain that tells the thyroid to work harder. A high TSH usually means the thyroid is underactive.
- Free T4 (FT4)
- The main hormone the thyroid makes. It is low when the thyroid is clearly underactive.
- Subclinical hypothyroidism
- TSH is raised but T4 is still normal. It is an early or mild change and may be watched or treated, depending on you.
- Thyroid nodule
- A lump within the thyroid gland. Most are not cancer.
- Anti-TPO antibodies
- A blood test showing the immune system is acting on the thyroid. It can help explain why the gland is underactive.
Leave a number, we will call you
One field. No form to fill in, and no charge for the call.
Commonly believed
What do survivors often believe about thyroid tablets?
"My thyroid test was normal after treatment, so I am past the risk."
Underactive thyroid can develop many years after neck radiation. A normal result is good news for now, and the yearly test is still needed.
"Once I feel better, I can stop the thyroid tablet."
Feeling better usually means the tablet is working. An underactive thyroid after radiation rarely recovers, and stopping brings symptoms back. Never stop or change the tablet on your own; your doctor adjusts it using blood tests.
"The tablet will make me put on weight or harm my heart."
The tablet replaces a hormone your body is missing. At the right level it does not cause weight gain. Too much can strain the heart, which is why regular tests keep the level right.
"Iodised salt or kelp will fix the thyroid."
Radiation damage is not caused by a lack of iodine. Extra iodine or seaweed supplements will not repair the gland and can sometimes upset thyroid tests.
Day to day
What should I know if I am put on thyroid tablets?
The usual treatment is levothyroxine, a daily tablet that replaces the missing hormone. Your doctor sets and adjusts the amount using blood tests, so it may take a few visits to find the right level. Take it the way your doctor explains, usually on an empty stomach and at the same time each day.
Things that can interfere with it
Iron and calcium tablets, some antacids and some other medicines can reduce how well the tablet is absorbed. Tell your doctor and pharmacist everything you take, including supplements and ayurvedic products, and ask how to space them.
Pregnancy and planning a family
Thyroid needs change in pregnancy. If you are planning a pregnancy or become pregnant, tell your doctor early so your levels can be checked and the treatment reviewed. An underactive thyroid that is not treated can make it harder to become pregnant and can affect the pregnancy, so this is one check worth doing before you start trying.
What this page cannot tell you
It cannot tell you whether your own result needs treatment, or what amount of tablet is right. That depends on your full results, symptoms, age and other conditions. Your haematologist, family doctor or an endocrinologist will guide you.
Questions we are asked
Common questions about the thyroid after neck radiation
How long after radiation can thyroid problems start?
They can start within a few years or appear many years later. The risk continues over a long time, which is why a yearly thyroid blood test is usually advised for life after radiation to the neck or upper chest, even if every result so far has been normal.
My TSH is slightly high. Does that mean I need tablets?
Not always. A slightly high TSH with a normal T4 is often repeated after a few weeks before any decision. Reference ranges differ between laboratories, and illness can change a single result. Your doctor will look at the trend, your symptoms and other tests before deciding.
Will I need thyroid tablets for the rest of my life?
Usually, yes, when the underactive thyroid is caused by radiation, because the gland rarely recovers. The tablet is taken daily, and the amount may need adjusting over the years. Regular blood tests keep it right. Many people take it for decades without problems.
Who should do my yearly thyroid test once haematology visits end?
Your family doctor or physician can arrange it. Make sure they know you had neck radiation for lymphoma and have a copy of your treatment summary. Some people set a reminder on their phone for the same month each year so the test is not missed.
I found a lump in my neck. Is it the lymphoma or the thyroid?
It could be a lymph node, a thyroid nodule or something harmless, and you cannot tell by feel. Report it to your haematology team. An examination, often an ultrasound scan, and sometimes a needle test will show what it is and whether anything needs doing.
Can an underactive thyroid be mistaken for chemo tiredness?
Very easily. Tiredness, low mood, weight gain and poor concentration are common after lymphoma treatment and are also signs of an underactive thyroid. A blood test separates the two, so ask for it rather than assuming the tiredness is just recovery.
Did chemotherapy alone affect my thyroid?
Chemotherapy alone is much less likely to cause long-term thyroid problems than neck radiation. Some newer treatments, such as certain immunotherapy drugs, can affect the thyroid, so tell your doctor exactly what you received and they will advise whether testing is needed.
Does neck radiation affect anything else I should check?
It can. Depending on the area treated, doctors may also watch the heart, the blood vessels of the neck, the teeth and, for women treated in the chest, breast screening. Ask your haematologist for a written list of the late-effect checks that apply to you.
Your Haematologist
Meet CION's haematologist. One specialist for your blood report and your plan.
Dr. Basudev Pokhrel reviews blood counts, transfusion needs and blood disorders, and works with the CION tumour board on blood cancers.
Want a specific doctor for your case? Mention them when booking.
Book Free ConsultationBook an appointment with our specialist
Share your name and number — we'll call you back within 30 minutes to schedule your consultation.
Patient stories
Hear it from people we have treated
Every story is a video, in the patient's own words. Nothing here is a written testimonial.
Sources
- NHS — Underactive thyroid (hypothyroidism)
- National Cancer Institute — Late Effects of Cancer Treatment
- Cancer Research UK — Hodgkin lymphoma
- American Cancer Society — Hodgkin Lymphoma
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.
Keep reading
Related pages
Talk to us
Had neck radiation for lymphoma?
Share your treatment summary and latest reports. Our haematology team will help you understand which checks you need.