Hypothyroidism, also known as underactive thyroid, is a common condition where your thyroid gland does not create enough of a thyroid hormone called thyroxine.
The thyroid gland is found in the front of the neck below the larynx (voice box) and has two lobes, one on each side of the windpipe. Hormones released by the gland travel through your bloodstream and affect nearly every part of your body, from your heart and brain, to your muscles and skin.
Thyroid hormones regulate your metabolism. This is the way your body uses energy and without enough thyroxine many of the body’s functions slow down. This means your body makes less energy and your metabolism becomes sluggish.
It is important to note the difference between hypothyroidism and hyperthyroidism (overactive thyroid) – a condition where the thyroid produces too much thyroxine.
What causes hypothyroidism?
- Hashimoto’s disease – This autoimmune disorder causes the body to produce antibodies that attack and destroy the thyroid gland. This leads to inflammation of the gland and interferes with its ability to produce thyroid hormones.
- Thyroiditis – This is the inflammation of the thyroid gland and it causes thyroid hormone to leak out into the blood stream. This raises the hormone levels and leads initially to hyperthyroidism. After a couple of months, this usually develops into hypothyroidism. Thyroiditis can be caused by bacterial or viral infection and can result from an autoimmune condition and pregnancy.
- Radiation therapy – This is often used to treat certain cancers such as Hodgkin’s disease and lymphomas. It damages cells in the thyroid making it more difficult for the gland to produce thyroxine.
- Radioactive iodine treatment – This is a common treatment for an overactive thyroid and works by destroying the cells of the thyroid gland thereby decreasing the production of thyroxine.
- Medications – A number of drugs can interfere with the production of thyroid hormone. These include amiodarone(Cordarone), lithium, interferon alpha, and interleukin-2.
- Too little iodine in the diet – Iodine is needed for the production of thyroid hormones. Your body doesn’t make iodine so you need to take it in through your diet. Iodised table salt is a rich source as are shellfish, saltwater fish, dairy products, eggs and seaweed.
- Thyroid surgery – Surgery to remove the thyroid will lead to hypothyroidism. If only part of the gland is removed, the remaining part may still be able to produce enough hormone for the body’s needs.
- Pituitary gland abnormalities – This gland makes a hormone called thyroid stimulating hormone (TSH) which tells your thyroid how much hormone it should make and release. Pituitary tumours or surgery can affect the function of the gland. If a woman loses a large amount of blood or has severe low blood pressure after childbirth, the gland can be damaged.
- Problems with the thyroid at birth – In cases of congenital hypothyroidism, babies are born with a thyroid gland that does not function properly.
Who is at risk of hypothyroidism?
Women, particularly older women, are more likely to develop the condition than men. This also applies if you have a close family member with an autoimmune disease. Other risk factors include:
- Age (growing older)
- Race (being white or Asian)
- Prematurely greying hair
- Autoimmune disorders such as type 1 diabetes, Coeliac disease, rheumatoid arthritis, multiple sclerosis, Addison’s disease, pernicious anaemia, lupus or vitiligo
- Down syndrome
- Bipolar disorder
- Turner syndrome
What are the signs and symptoms?
- Unexplained weight gain or difficulty losing weight
- Dry skin
- Thin brittle hair or fingernails
- Changes in the menstrual cycle including heavy periods
- Cold intolerance
- Slowed heart rate, increasing the risk of heart failure, especially in older women
- High blood pressure and raised levels of LDL cholesterol
- Swelling of the thyroid gland (goiter)
- Joint and muscle pain
- Puffy face, feet and hands
- Problems with balance, particularly in older women
Tests and diagnosis
If you have symptoms of hypothyroidism, your doctor will undertake a thorough physical examination, talk through your medical history and will order blood tests to check hormone levels.
The most common blood test is the TSH test. This detects the amount of thyroid stimulating hormone (TSH) in the blood. If the reading is above normal, then the patient is usually considered to have hypothyroidism. Low levels of TSH are usually an indication of an over active thyroid. Additional tests include the T4 test and the thyroid autoantibody test.
Treatment and prevention
If you are found to have the condition, your doctor will prescribe a synthetic thyroid hormone T4. This pill is to be taken every day and you will then need regular blood tests to check your thyroid hormone levels.
As certain other medications can interfere with how your body absorbs synthetic thyroid hormone, it is important that your doctor knows about all the medicines, supplements and over-the-counter products that you take.
Iodine is an essential mineral for the functioning of the thyroid. Iodine requirements increase in pregnancy so it is important to ensure that you take in sufficient by including iodised salt in your diet and take prenatal vitamins.
Diet can affect the way in which the body absorbs thyroid medication. Any major dietary change should be discussed with your doctor.
Hypothyroidism is usually able to be managed with medical advice and medications. These medications will usually need to be taken for the rest of the patient’s life.
If you would like help and advice please follow the link to the British Thyroid Foundation
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