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Hyperthyroidism (overactive thyroid)

Dr Karen Martin
Reviewed by Dr Karen MartinReviewed on 19.10.2023 | 3 minutes read

Hyperthyroidism means that your thyroid gland is functioning at a high or overactive level. The thyroid gland releases a hormone that helps control metabolism – if more hormone is released, your metabolism speeds up.

This can cause unintentional weight loss, your heart beats hard or fast, and you can feel twitchy, irritable or anxious. You may have difficulty sleeping although you feel very tired, and you might feel sweaty and hot all the time, perhaps wearing scanty clothing when others around you feel cold.

Your thyroid gland is a small gland in the front of your neck. In a chain reaction, your brain releases a hormone to prompt the thyroid gland to release a hormone (called thyroid-stimulating hormone or TSH) to produce thyroxine, also called free T4. This is the active substance controlling metabolism.

How do I know if I have it?

Discuss any of these symptoms in a routine appointment with your doctor. A blood test can assess thyroid function: if your free T4 is raised above normal and your TSH is low, this suggests you have hyperthyroidism.

Some people may have an enlarged thyroid gland, called a goiter, or little nodules, called a multinodular goiter. If very enlarged, this may be obvious to you, but your doctor will examine your neck for more subtle changes, and they may order a scan.

It can occur in anyone but is more common in women and those aged between 20 and 40. It may also occur alongside other autoimmune conditions, such as Type 1 diabetes or vitiligo, and these may run in the family.

What happens after diagnosis?

Your doctor will likely refer you to a specialist called an endocrinologist, who will assess your blood test and advise on treatment. Treatment options are designed to prevent the production of more thyroxine than necessary by the thyroid gland. They may start a medication to block thyroxine production, they may give radiotherapy – called radioiodine treatment – to prevent cells in the thyroid gland from producing thyroxine, or surgery may be necessary to remove some or all of the thyroid. If all of the thyroid is removed, you will be on lifelong thyroxine replacement.

Your symptoms and thyroid function will be monitored at regular intervals, depending on your treatment, and any medication doses tweaked as needed. It takes time for medications to change your thyroid function – weeks rather than days, and levels are typically re-checked no sooner than two months after any changes.

Your doctor might consider treatments to help alleviate symptoms, such as medication to slow a fast or irregular heart rate, or to alleviate any eye symptoms.

Once stabilized on treatment, your specialist may hand it over to your doctor to check your thyroid function every six to 12 months.

When should I seek urgent help?

Occasionally, you may experience a thyroid storm, which is a medical emergency. This is when hyperthyroidism is left untreated or inadequately treated. During this storm, your heart rate, blood pressure, and body temperature soar to very high levels, and this can be life-threatening if you don’t receive prompt treatment. If you feel unwell and you have been diagnosed with hyperthyroidism, go to the emergency department urgently.

Are there any long-term effects?

Grave’s disease is an autoimmune condition and a common cause of hyperthyroidism. This is confirmed by testing for an antibody in the blood. It may cause damage to the tissues behind the eyes, causing blurred vision, leaving them feeling gritty and sore, and they may bulge outwards. Smoking can make this worse. Your specialist will start targeted treatment to help this – if left untreated, changes may be permanent and there’s a risk of sight loss.

Hyperthyroidism in pregnancy is managed under specialist guidance, and levels are closely monitored to reduce risk to your baby.

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This article has been written by UK-based doctors and pharmacists, so some advice may not apply to US users and some suggested treatments may not be available. For more information, please see our T&Cs.
Dr Karen Martin
Reviewed by Dr Karen Martin
Reviewed on 19.10.2023
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