Thyroid conditions
The thyroid is a gland in the neck that regulates the body's metabolism. This page explains the symptoms of an underactive and an overactive thyroid, how they are found with a blood test, and how they are followed up.
What does the thyroid do?
The thyroid is a butterfly-shaped gland at the front of the neck. It makes hormones that set how the body uses energy. If it makes too little, we call it an underactive thyroid; if it makes too much, an overactive thyroid. Both are common, and both are found with a blood test.
Symptoms
Underactive thyroid. The sources list: unusual tiredness, feeling cold, weight gain, constipation, poor concentration, low mood, dry skin and hair, hair loss, a hoarse voice, and irregular or heavy periods. The condition develops slowly, and symptoms may go unnoticed for months or years.
Overactive thyroid. Nervousness and restlessness, poor sleep, tiredness and weakness, poor tolerance of heat, a pounding or irregular heartbeat, shaking hands, weight loss despite a good appetite, frequent bowel movements and a swelling in the neck (goitre). In older people the symptoms can differ, for example loss of appetite and withdrawal, and can be mistaken for depression.
Many of these symptoms are seen in other conditions too, so do not diagnose yourself.
How is it diagnosed?
The doctor asks about symptoms and family history (thyroid disease or autoimmune disease) and examines the neck. You then have a blood test:
- TSH. A hormone made by the gland under the brain that tells the thyroid how much hormone to make. The MedlinePlus source says a high TSH points to an underactive thyroid and a low TSH to an overactive one.
- T4 and sometimes T3. The thyroid’s own hormones, usually requested when the TSH is abnormal.
- Antibody tests to identify autoimmune conditions such as Hashimoto’s (a common cause of an underactive thyroid) and Graves’ (a common cause of an overactive thyroid), and sometimes imaging.
A TSH value alone does not show the cause. The MedlinePlus source says serious unrelated illnesses can lower it temporarily, it can be higher in people over 80, and it is slightly lower in the first three months of pregnancy. So ask the doctor how to read your number in the light of your age and circumstances, and do not compare it with other people’s.
Treatment
Underactive thyroid. Treatment is usually a replacement tablet, which supplies the hormone the thyroid does not make. The NHS source says it is usually lifelong and allows a normal life. Important points:
- The doctor sets the dose from your test results, and it may change over time.
- According to the NIDDK source, follow-up tests are done about 6 to 8 weeks after starting the medicine, after every change in dose, and then at regular intervals.
- Too much medicine can make the heartbeat irregular and weaken the bones. Tell the doctor or pharmacist about any side effect such as nausea, diarrhoea, headache or poor sleep.
- Do not stop thyroid medicine or change the dose yourself.
Overactive thyroid. The sources describe three general options: medicines that lower hormone production (anti-thyroid medicines), radioactive iodine and surgery. Some medicines only calm symptoms such as shaking and a pounding heart without reducing hormone production. The choice depends on the cause and your circumstances, including pregnancy and breastfeeding, and is made with the doctor or an endocrinologist. After radioactive iodine, the source says most patients later develop an underactive thyroid.
Follow-up and self-care
- Have your follow-up tests on time, even if you feel well.
- Always tell the doctor about all your medicines and supplements. The NIDDK source says too much iodine (for example from seaweed, some syrups or supplements) can cause an overactive thyroid. Ask the doctor before taking an iodine supplement or seaweed.
- Take the medicine at the time and in the way the doctor or pharmacist tells you (for example on an empty stomach or after a meal).
- If you are pregnant or planning a pregnancy, let the doctor know.
When should you call?
Contact the doctor if your heartbeat is fast or irregular, your weight changes suddenly, you have shaking, severe sleeplessness or new low mood, your neck is swollen or you notice a lump, or you have a side effect after starting a medicine.
In severe overactivity a “thyroid storm” can occur; the NHS source describes it as a sudden, dangerous flare-up of symptoms. If a person with an overactive thyroid suddenly becomes very unwell and symptoms get severe quickly, call 115 (the emergency number in Iran). Chest pain or pressure, sudden shortness of breath or signs of a stroke are also emergencies.
Every patient’s treatment plan is different; ask the doctor about your own situation.
Frequently asked questions
Do tiredness and hair loss mean I have a thyroid problem?
Not necessarily. The NIDDK source says many of these symptoms are common and do not always mean a thyroid problem. The diagnosis rests on an examination and a blood test, not on symptoms alone.
Do I have to take thyroid tablets forever?
The NHS source says treatment for an underactive thyroid is usually lifelong. Even so, any decision to continue or change the medicine belongs to the doctor alone. The NIDDK source also says: never stop thyroid medicine without talking to the doctor.
Why is the thyroid test repeated?
Because it is important to be sure the dose is right for your body. Too little or too much medicine causes symptoms, and too much can harm the heart and bones. The doctor sets the timing of the tests.
How does pregnancy change things with a thyroid condition?
If you have an underactive thyroid and you are pregnant or planning a pregnancy, tell the doctor. The NHS source says the dose may need to change during pregnancy; only the doctor makes that change. The MedlinePlus source also says the TSH reference range is slightly different in the first three months of pregnancy.
Is an overactive thyroid treated with medicine only?
No. The sources describe three general options: medicine, radioactive iodine and surgery. The choice between them depends on the cause, your age, pregnancy and your circumstances, and it is made with the doctor.