Hypothyroidism

What is the thyroid gland?

The thyroid gland sits at the front of the neck, just below the “Adam’s apple”. It produces two thyroid hormones, T3 (triiodothyronine) and T4 (thyroxine), which regulate how the body uses and stores energy — what we simply call “our metabolism”.

How well the thyroid works is controlled by another gland, the pituitary, which sits at the base of the brain. The pituitary produces thyroid-stimulating hormone (TSH), which stimulates the production of the thyroid hormones.

What is hypothyroidism?

When we say “I have hypothyroidism”, it means that our body has less thyroid hormone than it needs.

Hypothyroidism is the most common thyroid disorder. It is more common in women, becomes more frequent with age and is linked to an inherited predisposition. The symptoms are:

• tiredness
• depression
• sensitivity to cold
• weight gain (no more than 3–6 kg)
• dry skin, dry hair
• constipation
• menstrual disturbances

These symptoms are not unique to hypothyroidism, and many people with hypothyroidism may have only one or two of them. Fortunately, a simple blood test can diagnose hypothyroidism at an early stage.

What causes hypothyroidism?

• In adults, the most common cause is Hashimoto’s thyroiditis. In this condition, the immune system attacks the thyroid gland and gradually destroys it, so that it can no longer produce the thyroid hormones the body needs.
• Hypothyroidism can occur after radioactive iodine treatment or after surgical removal of the thyroid, if the patient does not take levothyroxine at the correct dose.
• A rare cause is the pituitary gland not working normally.
• Another cause is congenital hypothyroidism (that is, present from birth).

What are the effects of hypothyroidism?

In adults, uncontrolled hypothyroidism leads to memory problems and reduced physical fitness. In addition, blood cholesterol levels rise, with all the harmful effects this has on the heart. Rarely, in very severe hypothyroidism that remains uncontrolled for a long time, myxoedema coma can develop — a life-threatening condition.

How is it diagnosed?

We measure TSH and T4 in the blood, and diagnose hypothyroidism when TSH is raised and T4 is low. In early hypothyroidism, TSH is slightly raised while T4 is still normal (it has not yet had time to fall). Of the two tests, TSH is the more important, with the greater diagnostic value.

When the cause is Hashimoto’s thyroiditis, antithyroid antibodies should also be measured; these are the antibodies that attack the thyroid and cause the disease.

How is it treated?

Hypothyroidism is treated with thyroid hormone in tablet form. The treatment of choice is levothyroxine, which is made synthetically and is exactly the same as the T4 produced by the thyroid gland.

Because not all levothyroxine products are the same, a patient who is well controlled should ideally stay on the same product. If a change is nevertheless necessary, TSH should be measured before the switch and 40 days afterwards.

Overdosing (taking levothyroxine at a much higher dose than needed) over a long period can lead to loss of bone mass, especially after the menopause, as well as to problems with heart function and heart rhythm, especially in older people.

In pregnancy

Thyroid function should be checked before a woman conceives or as soon as she becomes pregnant, because throughout pregnancy, and above all in the first 10 weeks, thyroid control must be perfect. Otherwise, the developing baby and the outcome of the pregnancy are affected.

What should I do?

• If you have hypothyroidism, it is essential that you take your treatment consistently.
• If you have at least one of the symptoms above, or if there is thyroid disease in your family, ask your doctor for a blood test. If the result shows hypothyroidism, your first-degree relatives should also be tested.

It is a good idea:

1. for a woman to be tested as soon as she finds out she is pregnant;
2. for women over 60 to be tested, even if they have no symptoms.