Your thyroid is a small gland in the neck that sets the pace of your metabolism. When it makes too little hormone (hypothyroidism) you may feel tired, cold and sluggish; when it makes too much (hyperthyroidism) you may feel anxious, shaky and lose weight. A simple blood test, TSH, is usually the first step, and both conditions are very treatable once diagnosed.
Key takeaways
- About 1 in 10 adults in a large eight-city Indian study had hypothyroidism, and roughly a third of them did not know it.
- High TSH usually points to an underactive thyroid; low TSH usually points to an overactive one. Free T4 and sometimes T3 help confirm the picture.
- Women, people over 30 and those with a family history of thyroid disease are at higher risk.
- Using iodised salt protects against iodine deficiency, which India has long worked to eliminate.
- Thyroid hormone is vital for a baby's brain, so women with thyroid conditions should see their doctor as soon as they plan or confirm a pregnancy.
What the thyroid does
The thyroid makes two main hormones, thyroxine (T4) and triiodothyronine (T3). They influence heart rate, body temperature, energy use, digestion, mood, periods and many other functions.
The gland is controlled by the pituitary in the brain, which releases thyroid-stimulating hormone (TSH). When thyroid hormone is low, the pituitary sends out more TSH to push the thyroid to work harder. When thyroid hormone is high, TSH drops. This feedback loop is why TSH is such a useful screening test.
How common thyroid problems are in India
A cross-sectional study of 5,360 adults in eight Indian cities, published in 2013, found hypothyroidism in about 10.95% of participants. Of these, 7.48% already knew they had it, while 3.47% were newly detected.
The same study found higher rates in inland cities than in coastal ones, and the condition was linked with female sex and older age. Around one in five participants had anti-TPO antibodies, a marker of autoimmune thyroid disease.
Hypothyroidism: an underactive thyroid
Common symptoms
Symptoms usually come on slowly and can be mistaken for stress or ageing:
- Persistent tiredness
- Feeling colder than others around you
- Weight gain
- Constipation
- Poor concentration or memory
- Low mood
- Dry skin, dry hair or hair loss
- Hoarse voice
- Heavy or irregular periods
Main causes
The most common cause in many countries is Hashimoto's thyroiditis, where the immune system attacks the thyroid. Other causes include thyroid surgery, radiation to the neck, treatment for an overactive thyroid, some medicines and iodine deficiency.
How it is treated
Hypothyroidism is usually treated with a daily thyroid hormone tablet. Most people need it for life, and the dose is adjusted over time based on blood tests. Your doctor will decide the right dose; never change it on your own.
Hyperthyroidism: an overactive thyroid
Common symptoms
- Nervousness, anxiety or irritability
- Mood swings and trouble sleeping
- Tiredness and muscle weakness
- Feeling unusually hot or sweaty
- A fast or irregular heartbeat
- Trembling hands or twitching
- Weight loss despite eating normally
- A swelling at the front of the neck (goitre)
Main causes
Graves' disease, an autoimmune condition, causes most cases. Thyroid nodules that make extra hormone and some medicines, such as amiodarone, are other causes.
Treatment options include medicines that reduce hormone production, radioactive iodine and surgery. The best choice depends on the cause, your age and other health factors, and is decided with a specialist.
Reading your thyroid report
Lab reports list a reference range next to each result. Ranges vary slightly between labs and methods, so always compare your result with the range printed on your own report.
| Pattern | What it often suggests |
|---|---|
| High TSH, low free T4 | Hypothyroidism |
| High TSH, normal free T4 | Subclinical (mild) hypothyroidism |
| Low TSH, high free T4 and/or T3 | Hyperthyroidism |
| Low TSH, normal free T4 and T3 | Subclinical hyperthyroidism |
| Normal TSH | Thyroid usually working normally |
Other tests you may see
- Anti-TPO antibodies: Suggest autoimmune thyroid disease such as Hashimoto's.
- Thyroid ultrasound: Looks at the size of the gland and any nodules.
- Thyroid uptake scan: Helps find the cause of an overactive thyroid.
Things that can affect results
Serious illness can temporarily lower TSH. TSH tends to run a little higher in people over 80 without true thyroid disease, and it is often slightly low in the first three months of pregnancy. Some medicines and supplements, including biotin, can interfere with lab tests. Tell your doctor about everything you take, and do not stop medicines before a test unless your doctor asks you to.
A single borderline result is rarely a reason to start treatment. Doctors often repeat the test after a few weeks before deciding.
Iodine, iodised salt and the thyroid
The thyroid needs iodine to make its hormones. Long-term iodine deficiency can cause goitre, hypothyroidism and, in pregnancy, harm to the baby's brain development.
India's National Iodine Deficiency Disorders Control Programme aims for every household to use adequately iodised salt, defined as containing at least 15 parts per million (ppm) of iodine. WHO also advises that all salt used should be iodised.
Two practical tips help. Store salt in a closed container away from heat and moisture, because iodine can be lost over time. And remember that rock salt and many speciality salts are not iodised, so they should not replace iodised salt as your main kitchen salt.
More iodine is not better. Very high intake from seaweed or supplements can also upset thyroid function.
Thyroid health and pregnancy
Thyroid hormone is essential for a baby's brain and nervous system. In the first trimester, the baby relies fully on the mother's hormone. The baby's own thyroid begins working around 12 weeks but does not make enough until about 18 to 20 weeks.
If you already take thyroid medicine, you will probably need a higher dose during pregnancy. Contact your doctor as soon as you know you are pregnant, and expect thyroid tests every 4 to 6 weeks in the first half of pregnancy.
Iodine needs rise to about 250 micrograms a day during pregnancy. Ask your doctor about a prenatal supplement that contains iodine.
After delivery, about 1 in 20 women develop postpartum thyroiditis. It often starts with a brief overactive phase, then an underactive phase, and its symptoms can be confused with the "baby blues." Mention any lasting fatigue, low mood, palpitations or weight changes at your postnatal visits.
When to see an endocrinologist
Your family doctor can manage many cases of hypothyroidism. Ask for a referral to an endocrinologist if:
- You have hyperthyroidism or Graves' disease
- You have a thyroid nodule, goitre or a lump in the neck
- You are pregnant or planning pregnancy with a thyroid condition
- Your results remain abnormal despite treatment
- You have eye symptoms such as bulging, redness or double vision
- A child or teenager has abnormal thyroid tests
When to see a doctor
See a doctor soon if you notice a lump or swelling in your neck, persistent tiredness with weight change, a constantly racing heart, or a change in your periods with other thyroid symptoms. A neck lump that grows quickly or causes difficulty swallowing or breathing needs prompt attention.
Call 108 or 112 immediately if someone with a thyroid condition has a very fast or irregular heartbeat with high fever, confusion or agitation, or is extremely drowsy, very cold and confused. These rare situations can be life-threatening.
Frequently asked questions
What does a high TSH mean?
A high TSH usually means your thyroid is not making enough hormone, so the pituitary is pushing harder. Your doctor will check free T4 and may repeat the test to confirm. A mildly high TSH with normal T4 is called subclinical hypothyroidism and may only need monitoring.
Do I need to fast before a thyroid test?
Fasting is not usually required for a TSH test. Follow your lab's or doctor's instructions, and mention any supplements such as biotin, which can affect results.
Can thyroid problems cause weight gain or weight loss?
Yes. An underactive thyroid can cause modest weight gain, and an overactive thyroid often causes weight loss. Treatment helps, but thyroid disease is rarely the only reason for large weight changes.
Is thyroid disease curable?
Hypothyroidism is usually lifelong, but it is well controlled with daily medicine. Some types of hyperthyroidism can go into remission, and others are treated permanently with radioactive iodine or surgery. Your doctor will explain what to expect in your case.
Should I stop iodised salt if I have a thyroid problem?
Most people with thyroid disease should continue to use iodised salt in normal amounts. Your doctor may give special advice if you are having radioactive iodine treatment or have certain thyroid conditions.
Sources
- NHS: Underactive thyroid (hypothyroidism)
- NHS: Overactive thyroid (hyperthyroidism)
- MedlinePlus: TSH test
- NIDDK: Pregnancy and thyroid disease
- MoHFW DGHS: National Iodine Deficiency Disorders Control Programme
- Unnikrishnan AG et al. Prevalence of hypothyroidism in adults: eight cities of India, 2013
- American Thyroid Association: Hypothyroidism