Good health - Thyroids - Underactive thyroid and Overactive thyroid
What is the thyroid? The thyroid can be found in the front of your neck just below the Adam's apple and 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).
What causes thyroid problems?
Thyroid problems can result from either of the following causes:
Overactive thyroid - if the thyroid is overactive it produces too much T3 and T4, this condition is known as hyperthyroidism or thyrotoxicosis.
Underactive thyroid - if the thyroid is underactive it doesn't produce enough T3 or T4, this condition is known as hypothyroidism ('hypo' means under). An underactive thyroid is the most common thyroid problem and is more common in women and people over the age of 60, though the condition can be present at birth.
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:
Swelling in the neck due to an enlarged thyroid (goitre)
Rapid or irregular heartbeat.
Insomnia - trouble sleeping.
Weight loss in spite of increased hunger.
Women may experience irregular periods and a lighter menstrual flow. Irritated and puffy eyes is a symptom which may be seen in people with Grave's disease. In severe cases it can lead to excessive bulging - swelling of the eyes with a distinct stare (caused by the upper eyelids being elevated), which in extreme cases can cause problems with vision.
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
Feeling tired and lacking energy.
A tendency to feel the cold more than healthy people.
Heart may beat slower.
Weight gain and difficulty in losing it.
Irregular or heavy periods.
A hoarse, croaky voice.
Later symptoms may include constipation, dry, pale skin and dry hair, which may be brittle and break easier.
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.
If inflammation of the thyroid gland is suspected, an ultrasound scan of the gland may also be taken.
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:
Medication for thyroid problems - this stops or reduces the thyroid from making too much thyroid
hormone. The length of time medication is required depends on the cause of the
Surgery - most of the thyroid is removed and after the operation most people make a full recovery. However, a small amount of people may then go on to develop hypothyroidism.
Radioactive iodine - this is simple, safe and painless, you simply take a single drink of tasteless radioactive iodine or a capsule. This treatment is aimed at shrinking the thyroid gland and so reducing the activity. The treatment is safe and metabolism usually returns to normal within months.
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.
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