Thyroid gland
The thyroid gland is situated in the front of the neck, on either side of the trachea (windpipe).
This gland makes a hormone (thyroxine) which is secreted directly into the bloodstream and goes to all parts of the body.
Thyroxine affects the body's metabolic rate — the rate at which we function. Too much of it produces a rapid heart rate, sweating and weight loss. The affected person may seem nervous and ‘jumpy’, and there may be an obvious tremor (shaking) of the hand. Too little thyroxine produces the opposite picture. A slow, sluggish individual who can't lose weight, tends to be constipated and has dry skin is the typical picture. There may be hair loss and the voice may get deeper.
Both of these conditions are more common in females than males.
What happens when you have an overactive thyroid?
Too much thyroxine causes a condition called hyperthyroidism, or thyrotoxicosis. As well as the symptoms mentioned above, the sufferer may have a generalised swelling of the thyroid, known as goitre, and a ‘pop-eyed’ appearance.
Sometimes the cause of an overactive thyroid is an auto-immune problem, and it can also occur as a temporary state following a virus-like illness.
The treatment of thyrotoxicosis may be by using drugs which suppress the formation of thyroxine, by using radioactive iodine (taken as a drink, which selectively destroys the gland) or by surgery (removing all or most of the gland).
What happens when you have an underactive thyroid?
Inadequate production of thyroxine is called hypothyroidism or myxoedema. It is especially common in women over the age of 50 years.
It usually happens gradually and can easily be mistaken for the generalised slowing down that we can all expect as we get older. A wide variety of symptoms may be present due to the fact that thyroxine has some effect on just about all parts of the body.
Treatment consists of taking thyroid hormone tablets, usually for the rest of your life.
Children may be born with deficiency of their thyroid gland. If not detected this can cause problems with their physical and mental development. Babies are routinely tested for low thyroid function shortly after birth.
Other thyroid conditions
As well as abnormalities in the production of its hormone, the thyroid gland can be affected by other diseases. Thyroid cancer shows up as a firm, usually painless, lump in the thyroid. Harmless cysts may occur and goitre is seen in places where there is a deficiency of iodine in the diet.
Thyroid diseases may be diagnosed by blood tests, scans, and ultrasound. Most of them can be treated very effectively. As with many diseases, early diagnosis is best. If you have noticed any swelling in the neck, or have experienced the symptoms of too little or too much thyroxine mentioned above, talk to your doctor.
Last Reviewed: 04 June 2008
