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The thyroid gland is situated at the front of the throat, below the Adam’s apple (larynx). It comprises two lobes that lie on either side of the windpipe, joined in front by an isthmus. The thyroid gland secretes hormones to regulate many metabolic processes, including growth and energy expenditure. Hypothyroidism means the thyroid gland is underactive and fails to secrete enough hormones into the bloodstream. This causes the person’s metabolism to slow down. Hypothyroidism is the most common thyroid disorder, and it is thought to affect around six to 10 per cent of women. The prevalence rises with age - up to a quarter of women over the age of 65 years may be affected. Men are also affected, but less frequently. Hypothyroidism can be either primary or secondary. Primary hypothyroidism means that the thyroid gland itself is diseased, while secondary hypothyroidism is caused by problems with the pituitary gland, the brain structure that supervises the thyroid gland. The most common cause of primary hypothyroidism is the autoimmune condition Hashimoto’s disease. Symptoms of hypothyroidismThe symptoms of hypothyroidism can be mild, moderate or severe. In its severest form (myxoedema coma), hypothyroidism is potentially fatal and requires urgent medical treatment. Symptoms of hypothyroidism can include:
The thyroid hormonesThe pituitary gland, located in the brain, prompts the thyroid to make its hormones by releasing thyroid stimulating hormone (TSH). The thyroid gland makes two main hormones - thyroxine (T4) and tri-iodothyronine (T3). These hormones contain atoms of iodine. Around 150 mcg (millionths of a gram) of dietary iodine is needed each day to produce adequate levels of thyroid hormones. Seafoods are particularly rich in iodine.Causes of hypothyroidismThe causes of hypothyroidism include:
Diagnosis of hypothyroidismHypothyroidism is diagnosed by physical examination and blood tests. The doctor may also order ultrasound or radioactive iodine scans to check the internal structure of the thyroid.Treatment for hypothyroidismIodine deficiency can be easily relieved by increasing the intake of iodine through iodised salt or iodine rich foods. Hypothyroidism may be caused by the failure of - or damage to - the thyroid gland, pituitary or hypothalamus. In these cases, treatment focuses on boosting thyroid hormone levels with thyroxine tablets, a form of hormone replacement.From underactive to overactiveThere is no cure for autoimmune hypothyroidism, so medication will have to be taken for the rest of the person’s life. The dose must be carefully monitored. Too little medication won’t relieve the symptoms. Too much medication can result in hyperthyroidism (resulting from too much thyroxin). It is important to see your doctor if you experience any symptoms of hyperthyroidism, including:
Where to get helpThings to remember
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This page has been produced in consultation with and approved by:
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