Hypothyroidism is a condition where the thyroid gland produces too little thyroid hormone for the body’s needs. It is also known as an underactive thyroid.

• Hypo - means 'under -'
  
  
• Hyper - means 'over -'

Content overview

Causes

Common symptoms

Diagnosis

Treatment

Follow-up

Further information

Causes

• Autoimmune thyroid disease sometimes called Hashimoto’s thyroiditis
  
  
• Radioactive iodine or surgery to correct hyperthyroidism or thyroid cancer
  
  
• Over-treatment of hyperthyroidism with antithyroid drugs
  
  
• Some medicines, e.g. lithium, amiodarone, pembrolizumab or nivolumab
  
  
• Some health foods, e.g. kelp (seaweed)
  
  
• A malfunction of the pituitary gland
  
  
• Sometimes hypothyroidism is present at birth

Common symptoms

A slowing down of mental and physical processes of the whole body such as:

• Fatigue and tiredness
  
  
• Weight gain
  
  
• Increased awareness of the cold
  
  
• Constipation
  
  
• Dry skin and hair
  
  
• Low mood or depression
  
  
• Memory or concentration difficulties (sometimes referred to as ‘brain fog’)
  
  
• Heavy periods and fertility problems
  

Diagnosis

• By a physical examination and blood tests
  
  
• A high thyroid stimulating hormone (TSH) level with a low thyroxine (T4) level indicates hypothyroidism. Rarely, hypothyroidism can occur when both the TSH and T4 are low
  
  
• A slightly raised TSH with a normal T4 is called subclinical, mild, or borderline hypothyroidism
  
  
• Subclinical hypothyroidism can develop into clinical or overt hypothyroidism

Treatment

• Levothyroxine tablets (a synthetic version of thyroxine) taken daily, for life
  
  
• Tell your doctor if you are taking any other medicines or special foods as some can interfere with levothyroxine absorption
  
  
• It is important to take your tablets consistently every day as failure to do this can affect your blood test results and your health
  
  
• If you are planning a baby, let your doctor know and ideally have a blood test before you conceive. As soon as you know you are pregnant, and if you are already taking levothyroxine, it is recommended that the levothyroxine dose is increased immediately. This is often achieved by doubling the dose on two days of the week, or by a daily 25-50mcg increase. You should then arrange follow up blood tests

Follow-up

Blood tests are carried out

• Approximately every six to eight weeks after the start of therapy or after a dose change until the correct dose of levothyroxine is established (i.e. the TSH is within the normal reference range)
  
  
• Once a year thereafter (except in special circumstances such as pregnancy when more frequent testing is required) 

Further information

Read our guide to hypothyroidism

Find information about treatments for hypothyroidism

Read about subclinical hypothyroidism

Living better with hypothyroidism article

Useful resources (films, patient stories, articles, events, phone support etc.)

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