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Underactive Thyroid

An underactive thyroid is one which produces too little thyroid hormone (‘thyroxine’). This can cause a wide range of symptoms, including severe complications if left untreated.

What is an underactive thyroid?

An underactive thyroid, also known as hypothyroidism, is a condition in which the thyroid gland produces too little thyroid hormone.

The thyroid is a small, butterfly-shaped gland in the neck, just in front of the windpipe. It produces hormones to help regulate many processes in your body.

Too little of this hormone can affect your entire body and cause a range of symptoms.

What are the symptoms of an underactive thyroid?

Here are some of the more common symptoms related to having an underactive thyroid:

  • Fatigue
  • Sensitivity to the cold
  • Slowed heart rate
  • Weight gain
  • Constipation
  • Depression
  • Slow movements and thoughts
  • Muscle weakness
  • Muscle aches and cramps
  • Dry skin
  • Brittle hair and nails
  • Loss of libido
  • Pain, numbness and tingling in hands
  • Menstrual changes
  • Pale, puffy face

People over 60 may also develop memory problems, while children may experience slower growth and development. It can also cause puberty to start earlier than normal.

If left untreated it can lead to complications including heart disease, goitre, difficulty conceiving and pregnancy problems and even, in extreme cases, coma.

If you are concerned about your symptoms, you should visit your GP.

What causes an underactive thyroid?

There are several reasons why you might have an underactive thyroid:

  • Hashimoto’s disease (an autoimmune condition)
  • Thyroiditiis (inflammation of the thyroid gland) due to infection
  • Congenital hypothyroidism
  • Treatment of the thyroid, including surgical removal or radiation
  • Some medicines (several are implicated including carbimazole, amiodarone, lithium)
  • Disorders of the pituitary gland or hypothalamus
  • Iodine deficiency

Risk factors include:

  • Female gender
  • Age over 60 years
  • Family history of thyroid problems
  • A personal history of thyroid problems
  • Pregnancy within the last 6 months
  • A number of autoimmune conditions including Coeliac disease, Sjögren’s syndrome, pernicious anaemia, Type 1 or 2 diabetes, rheumatoid arthritis, and lupus

How is an underactive thyroid diagnosed?

If you have been experiencing underactive thyroid symptoms, you should speak to your GP or an endocrinologist (specialist in the management of hormone disorders).

At your appointment, you will be asked about your symptoms, other medical conditions, medication, family history and other factors such as your work and whether you smoke cigarettes. Your GP or Consultant may do a physical examination of your neck, as well as examine other areas of your body that have been affected.

If they think there is a thyroid issue, they will arrange for a blood test, which will let them know how well your thyroid is working.

How is an underactive thyroid treated?

The treatment for an underactive thyroid involves taking daily hormone replacement tablets (levothyroxine).

You will need regular blood tests to monitor your hormone levels, and usually treatment is required for life.

If you’re unsure what treatment you should go for, or the above treatments don’t work for you, our team of expert specialists are here to help.

This content has been checked and approved by

Miss Aimee Di Marco  ›

Miss Aimee Di Marco is an Endocrine Surgeon at King Edward VII’s Hospital.

Find your specialist in underactive thyroids at King Edward VII's Hospital

Dr Malcolm Prentice  ›
Special interests include:
Diabetes (+ 18) more
Miss Aimee Di Marco  ›
Special interests include:
Parathyroid surgery (+ 11) more

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