What is hypothyroidism?
The thyroid is a butterfly-shaped gland in the front of the neck. It makes hormones that control how fast the body uses energy, affecting the heart, brain, gut, skin and periods. In hypothyroidism, the gland makes too little hormone, so the body slows down.
It is common in India, especially in women, and becomes more frequent with age. It can also appear during or after pregnancy, and it sometimes runs in families. Once it is properly treated, most people feel normal again, their energy returns, and they lead a full and active life.
Causes
The most common cause is an autoimmune condition called Hashimoto's thyroiditis, where the body's own defence system slowly damages the thyroid. Other causes include thyroid surgery, radioactive iodine treatment, some medicines, and iodine deficiency, which is less common now that iodised salt is widely used. Some babies are born with an underactive thyroid, which is why newborn screening is done.
Hypothyroidism is more likely if you have a family history of thyroid disease or another autoimmune condition such as type 1 diabetes, vitiligo or rheumatoid arthritis. Women are affected more often than men, and the risk rises after the age of 40 and in the months after childbirth.
Symptoms of hypothyroidism
Symptoms come on slowly over months or years and are easy to blame on stress, age or a busy life. Some people have very mild symptoms or none at all, and are found only on a routine blood test. Common symptoms include:
In children, an underactive thyroid can slow growth, delay puberty and affect school performance. In older adults, it may show up mainly as forgetfulness, low mood or high cholesterol. Because the signs are so general, a simple blood test is the best way to find out.
- Tiredness, low energy and sleepiness
- Weight gain without eating more
- Feeling cold when others are comfortable
- Dry skin, hair fall and brittle nails
- Constipation
- Heavy or irregular periods, or difficulty conceiving
- Low mood, poor memory or slow thinking
- Puffy face, swelling of the neck (goitre) or muscle aches
Tests and diagnosis
The main test is TSH (thyroid stimulating hormone). When the thyroid is underactive, the brain releases more TSH to push it, so TSH goes up. Free T4 is measured to see how much thyroid hormone is actually in the blood. Anti-TPO antibodies may be checked to find out if the cause is autoimmune.
A slightly raised TSH with a normal T4 is called subclinical hypothyroidism. Your doctor may repeat the test after some weeks before deciding on treatment, since mild changes can settle on their own after an illness. Treatment is more likely if you are pregnant or planning pregnancy, have symptoms, or have positive antibodies.
How hypothyroidism is treated
Treatment is a daily tablet of levothyroxine, which replaces the missing hormone. It is taken only on a doctor's prescription, and the dose is adjusted based on TSH tests, usually rechecked several weeks after any change. Most people need it for life. Do not stop or change the dose on your own, even when you feel better.
Take the tablet on an empty stomach with water, at the same time each day, and wait before breakfast or tea as your doctor advises. Keep calcium, iron and antacid tablets separate by a few hours, since they reduce absorption. Tell your doctor about all other medicines you take.
Buy the same strength and, where possible, the same make of tablet each time, because switching can change your levels slightly. If you change, get your TSH rechecked. Store tablets in a cool, dry place away from direct sunlight, and never double up if you miss a dose without asking your pharmacist.
Pregnancy, children and older adults
Thyroid hormone is vital for a baby's brain development. Women with hypothyroidism who are planning pregnancy or become pregnant should inform their doctor at once, as the dose often needs to increase early in pregnancy. Levothyroxine is safe in pregnancy and breastfeeding. Children with low thyroid need prompt treatment for normal growth.
In older adults and people with heart disease, doctors usually start with a low dose and increase it slowly to avoid strain on the heart. If you have any doubts about your tablet, the right timing, missed doses or when to repeat your tests, talk to your doctor or pharmacist.
Medicines doctors commonly use
Only your doctor can decide which medicine, dose and combination is right for you.
- Levothyroxine (thyroid hormone replacement)Replaces the thyroid hormone the gland cannot make, restoring normal body functions.Only on a doctor's prescription; too much can cause palpitations, weight loss and bone thinning, so regular TSH checks matter.
- Iron and calcium supplementsSometimes needed alongside, for example in pregnancy or anaemia.Take them several hours apart from levothyroxine, as they block its absorption.
See a doctor urgently if
- Extreme drowsiness, confusion, very slow heart rate or feeling very cold, especially in elderly people
- Chest pain, fast or irregular heartbeat after starting or increasing thyroid tablets
- Pregnancy or planned pregnancy while on thyroid treatment, without a recent TSH check
- A new lump in the neck, rapid swelling, or difficulty swallowing or breathing
- Severe depression or thoughts of self-harm
Tests that may help
This article is general health information, not medical advice. Do not start, stop or combine medicines on your own — always follow your doctor's prescription and ask your pharmacist if unsure.