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Thyroid Gland (TSH)


The Thyroid Gland?

The thyroid gland is a small butterfly shaped gland which can be found in the front of your neck just in front of the windpipe, below the Adam’s apple. This is where hormones are produced and released into the bloodstream. The major hormones the thyroid 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 (‘hyper’ means over) 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.
  • Goitre- an abnormal swelling of the thyroid gland.
  • Thyroid cancer – this is quite rare in the UK but if you have any lumps in your neck you should get these checked by your doctor.

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 and is also more common in people who smoke cigarettes.

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 (underactive thyroid)?

Hypothyroidism can occur in both men and women, however, it’s more common in women. Most cases are caused by the immune system attacking the thyroid gland and damaging it. 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, used to treat certain mental conditions and Amiodarone, used to treat irregular heartbeats.

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 and are caused by a speeding up of processes in the whole body:

  • Trouble concentrating.
  • Mood swings.
  • Swelling in the neck due to an enlarged thyroid (goitre)
  • Rapid or irregular heartbeat.
  • Trembling hands.
  • Excessive sweating and heat intolerance.
  • Insomnia – trouble sleeping.
  • Tiredness
  • Thirst
  • 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 following:

  • 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.
  • Forgetfulness.
  • Loss of sex drive.
  • Pain, numbness and a tingling sensation in hands and fingers.
  • Depression.

Later symptoms may include constipation, hearing loss, anaemia, dry, pale skin and dry hair, which may be brittle and break easier.

Symptoms in children may include a slower growth and development and teenagers may start puberty earlier.

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 will 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. You will probably need treatment for the rest of your life. Treatment available may include one of the following:

  • Medication – 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 illness. Due to the effectiveness of medication this is usually the treatment given.
  • 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 or swallow a tablet of tasteless radioactive iodine. 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. However, as your body gets rid of the iodine it’s important to be careful about the contact you have with other people, this will depend on the amount you were given. Your doctor will give you more advice.

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.

What are the long term effects of hyperthyroidism?

The long term effects will vary depending on the cause of hyperthyroidism. If Graves disease is the cause then you might experience eye problems such as bulging, swollen or red eyes and they may be watery and sensitive to light. If hyperthyroidism is left untreated it can also lead to you developing an underactive thyroid. A major complication of untreated hyperthyroidism is ‘thyroid storm’, this is a potentially life threatening condition but fortunately quite rare. Thyroid storm causes a persons heart rate, blood pressure and temperature to raise to dangerously high levels, this is caused by thyroid levels becoming very high.

What are the long term effects of hypothyroidism?

When treated hypothyroidism is manageable and people can lead normal lives and complications can be avoided. However, left untreated it can lead to complications  including heart disease, goitre, pregnancy problems and even a rare life threatening condition called myxoedema coma. This occurs when thyroid hormone levels drop very low.

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.

If an underactive thyroid isn’t treated during pregnancy there is a risk of pre-eclampsia, stillbirth, miscarriage, anaemia, birth defects or an underactive thyroid in the baby.

The good news is most babies will be born with completely normal thyroid function even if you developed thyroid problems during pregnancy.

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.