The thyroid is a small butterfly shaped gland where hormones are produced and released into the bloodstream. The major hormones the gland makes are called T4 or thyroxine and T3 or triiodothyronine. The production of these hormones are stimulated by another hormone called thyroid stimulating hormone (TSH).
The thyroid hormones are very important as they control the rate at which the body uses and stores energy from the food we eat (the metabolic rate).
The thyroid can be found in the front of your neck just below the Adam’s apple.
What causes thyroid problems?
Thyroid problems can result from either of the following causes:
What causes hyperthyroidism (overactive thyroid)?
There are several causes of hyperthyroidism, the most common is an autoimmune disease called Graves’ disease or diffuse toxic goitre (see below). Graves’ disease occurs when antibodies , which are usually produced to fight infections stimulate the thyroid gland into producing increased amounts of thyroid hormones. This usually causes the thyroid gland to become enlarged, called a goitre. Scientists are not exactly sure what causes Graves’ disease though it does tend to be an inherited condition, especially among female members. Graves’ disease may also be triggered by stress.
In the elderly a condition called toxic nodular goitre may cause hyperthyroidism. Toxic nodular goitre occurs when one or more small benign tumours in the thyroid gland produce excess thyroid hormones.
The thyroid gland may also become inflamed for unknown reasons or due to a viral infection, the inflamed gland can cause excess thyroid hormones, stored in the gland, to leak into the bloodstream. This is usually a temporary condition and usually clears up within 6 months, though a period of hypothyroidism may follow before recovery is made.
What causes hypothyroidism (underacive thyroid)?
In babies it is not known what causes hypothyroidism. In older children and adults the most common cause of hypothyroidism is due to the autoimmune disease, called Hashimoto’s disease, which tends to run in families. An autoimmune disease occurs when the immune system, which normally produces antibodies to attack foreign substances (like viruses and other bugs), starts producing antibodies which attack part(s) of the body. In people with hypothyroidism the immune system attacks the thyroid cells as if they were foreign substances.
Other possible causes may include complications from previous thyroid surgery, treatment for previous hyperthyroidism or certain medications, such as Lithium and Amiodarone.
Iodine and the thyroid
The thyroid gland must have iodine to make the thyroid hormones. Iodine comes into the body in food we eat and travels through the blood to the thyroid. Iodine is a mineral that is found naturally in foods like seafood and milk. Iodine can also be found in some mineral supplements that contain or are made from kelp (a kind of seaweed), cough syrups and some medications (Amiodarone).
A diet which is high in iodine can sometimes cause hyperthyroidism and if you have a problem with your thyroid, such as Graves’ disease then excess iodine can make the condition worse.
A lack of iodine in your diet can trigger hypothyroidism. This is rare in the western world as iodine is added to table salt, but in less developed countries iodine deficiency is the most common cause of hypothyroidism. To the other extreme, high intakes of iodine can occasionally prevent the thyroid gland from working properly.
The thyroid and pregnancy
During pregnancy your immune system is suppressed as a protection for the baby but after delivery there is a rise in immune activity and this can trigger a thyroid disease to develop or make a thyroid disease worse. If you or a close relative has ever had an over or under active thyroid you should tell your doctor when you find out you are pregnant, so that your thyroid levels can be checked during and after pregnancy.
Hyperthyroidism or hypothyroidism is most common in the first 2-3 months after pregnancy. However, it will often go undetected with the normal body changes and confusion that occurs after child birth. If pregnancy has triggered a thyroid disease it is usually temporary and may last 3-6 months before a full recovery is made.
The good news is most babies will be born with completely normal thyroid function even if you developed thyroid problems during pregnancy.
What are the symptoms of hyperthyroidism?
In hyperthyroidism the thyroid is overactive and so the rate of metabolism speeds up, the symptoms you experience may include any of the following:
What are the symptoms of hypothyroidism?
In hypothyroidism the thyroid is underactive and so the rate of metabolism slows down. As hypothyroidism usually develops slowly you may have no symptoms until the condition is well advanced. The symptoms you may have might be blamed on old age and can vary in severity but as your metabolism continues to slow, the symptoms should become more obvious. The symptoms may include any of the following:
How are thyroid problems diagnosed?
Your doctor may be able to make a diagnosis from your history, symptoms and an examination, though a blood test should be carried out to confirm the diagnosis. The blood tests will check the levels of TSH (thyroid stimulating hormone), T3 and T4 in the blood. These tests are known as thyroid function tests. If the blood tests show levels of TSH are raised then the thyroid gland is underactive, this is because TSH levels rise to try to manufacture more T3 and T4. The same is true in reverse, if the thyroid is overactive and producing above normal levels of T3 and T4 then less TSH is produced.
What is the treatment for hyperthyroidism?
If your doctor diagnoses you with hyperthyroidism, the treatment you receive will depend on your age, physical condition and the severity of the condition and may include one of the following:
What is the treatment for hypothyroidism?
If you have been diagnosed with hypothyroidism you will need to take thyroxine tablets, a thyroid hormone supplement, which simply replaces the thyroid hormone T4 which is not being made. Occasionally you may be given T3 replacement tablets as an alternative.
This treatment will need to be taken for life even though you should begin to feel better. Your doctor will want to monitor your condition with regular blood tests to check the thyroid hormone levels and how the treatment is working.