What is hyperthyroidism?
The thyroid gland in the neck makes hormones that set the speed of the body's metabolism. In hyperthyroidism, the gland makes more hormone than needed, so everything speeds up: the heart beats faster, food is burnt quickly and the nerves feel on edge.
It is more common in women and often starts between the ages of 20 and 50, though it can happen at any age. Without treatment, it can lead to heart rhythm problems, weak bones and, rarely, a dangerous condition called thyroid storm.
The good news is that hyperthyroidism responds well to treatment. Once hormone levels are brought back to normal, the heartbeat settles, weight returns and sleep improves. The key is to find it early, follow your doctor's plan closely and keep up with blood tests, since the right dose changes over time.
Common causes of hyperthyroidism
The most common cause is Graves' disease, an autoimmune condition in which the body's defence system makes antibodies that push the thyroid to overwork. It often runs in families and can also affect the eyes, making them bulge, feel gritty, water or look red. The main causes are:
Less often, too much iodine from supplements or certain medicines, such as amiodarone used for heart rhythm problems, can trigger an overactive thyroid. Temporary thyroiditis after childbirth can cause a short overactive phase followed by an underactive one, so new mothers with symptoms should get tested.
- Graves' disease
- Toxic nodules: one or more lumps in the thyroid making extra hormone
- Thyroiditis: inflammation of the gland, sometimes after a viral illness or pregnancy, often temporary
- Taking too much thyroid hormone tablet
Symptoms of hyperthyroidism
Symptoms can be mistaken for stress or anxiety. Common signs include weight loss despite a good appetite, a fast or pounding heartbeat, sweating and feeling hot, trembling hands, nervousness and irritability, poor sleep, frequent loose motions, tiredness and muscle weakness, and lighter or fewer periods.
Some people notice a swelling in the front of the neck, called goitre. Older people may have fewer symptoms, sometimes only tiredness, weight loss, low mood or an irregular heartbeat called atrial fibrillation. Because the signs can look like anxiety or stress, a blood test is needed to be sure.
How hyperthyroidism is diagnosed
Blood tests are the first step. In most cases TSH is low, because the brain stops asking for more hormone, while free T4 and free T3 are high. Your doctor may also order TSH receptor antibodies to confirm Graves' disease, and a blood count and liver tests before starting medicines.
A thyroid scan or ultrasound may be used to see whether the whole gland or a nodule is overactive, and to look at lumps. An ECG may be done if your heartbeat is fast or irregular. These tests help your doctor choose the right treatment.
Treatment options for hyperthyroidism
Treatment depends on the cause, your age, pregnancy plans and personal choice. Anti-thyroid tablets reduce hormone production and are often the first step. Beta blockers may be used for a short time to control a racing heart and tremor. All these are taken only on a doctor's prescription, with regular blood tests to adjust the dose.
Some people need radioactive iodine, which slowly shrinks the overactive gland, or surgery to remove part or all of the thyroid. After these treatments, many people become hypothyroid and need lifelong thyroid hormone tablets. Temporary thyroiditis often needs only symptom control.
Anti-thyroid tablets are usually given for many months, and the dose is reduced as hormone levels settle. Never stop them suddenly on your own, as symptoms can return quickly. Tell your doctor about any rash, joint pains or yellowing of the eyes, as these can be side effects that need a change of treatment.
Pregnancy, self-care and follow-up
Hyperthyroidism in pregnancy needs close care by a doctor, because both the condition and some treatments can affect the baby. Radioactive iodine is not used in pregnancy or breastfeeding. Tell your doctor at once if you become pregnant or plan to.
Eat a balanced diet with enough protein and calcium to protect your muscles and bones. Stop smoking, which worsens thyroid eye disease. Keep follow-up appointments and blood tests even when you feel better. Ask your doctor or pharmacist about side effects to watch for with your medicines.
Medicines doctors commonly use
Only your doctor can decide which medicine, dose and combination is right for you.
- Anti-thyroid medicines such as carbimazole, methimazole or propylthiouracilReduce the amount of thyroid hormone the gland makes.Stop and see a doctor urgently if you get fever, sore throat or mouth ulcers, which can signal a rare drop in white blood cells.
- Beta blockers such as propranololControl fast heartbeat, tremor and anxiety while the thyroid settles.Only on a doctor's prescription; used with caution in asthma.
- Radioactive iodineA one-time treatment that slowly reduces thyroid activity.Not given in pregnancy or breastfeeding; pregnancy should be avoided for a period your doctor advises.
- LevothyroxineReplaces thyroid hormone if the gland becomes underactive after treatment.Only on a doctor's prescription, with regular TSH checks.
See a doctor urgently if
- High fever, sore throat or mouth ulcers while taking anti-thyroid tablets
- Very fast or irregular heartbeat, chest pain or breathlessness
- High fever with confusion, agitation, vomiting or diarrhoea, which may be thyroid storm
- Yellow eyes or skin, dark urine or severe belly pain while on treatment
- Eye pain, double vision or sudden change in vision
- Rapidly growing neck swelling or difficulty breathing or swallowing
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.