Anna Garidou

The thyroid is a gland everyone has, and it is vital to our health. When people say they “have thyroid”, they usually mean they have a thyroid condition. The most common are:

• hypothyroidism (a functional disorder)
• hyperthyroidism (a functional disorder)
• thyroid nodules (a structural disorder)

To find out whether there is a problem, you need specialised blood tests and a thyroid ultrasound.

Only an underactive thyroid lowers your basal metabolic rate (you burn fewer calories), in proportion to how severe it is — so it may lead to gradual weight gain.

Once an underactive thyroid is diagnosed and treated correctly, though, there is no reason to gain weight. The same applies if your thyroid has been removed, as long as your treatment is well adjusted.

Nervousness or irritability together with a fast heartbeat, insomnia, tremor, sweating, intolerance to heat, tiring easily, weight loss and often muscle weakness can be explained by untreated hyperthyroidism — or, to a lesser degree, by too high a dose of thyroxine.

If your thyroid blood tests are normal, however, your nerves are not caused by your thyroid.

A nodule is a lump within the thyroid, usually benign (85–90%). It can range from a few millimetres to a few centimetres; under one centimetre it is considered small, but it still needs monitoring. There may be a single nodule or several.

A cold nodule does not produce hormones; 85% of cold nodules are benign. A hot nodule overproduces hormones; hot nodules are almost always benign.

Investigation involves specialised blood tests (TSH, FT3, FT4, thyroglobulin, calcitonin), a colour Doppler ultrasound and, if the endocrinologist considers it necessary, a fine-needle aspiration. Read more about thyroid nodules.

A goitre is an enlarged thyroid gland. The enlargement accompanies many thyroid conditions. When there is enlargement only, with no other condition, it is called a simple goitre.

If there is no underlying heart disease, a thyroid-related fast heartbeat is caused by hyperthyroidism — an excess of thyroid hormones.

If you have heart failure, coronary heart disease, an arrhythmia or atrial fibrillation and also take thyroxine, a fast heartbeat can occur even when hormone levels are normal. The dose should then be kept as low as possible.

• Hyperinsulinaemia
• The years leading up to the menopause
• Recent menopause
• An adrenal adenoma

As well as other, rarer endocrine conditions.

If the whole gland has been removed, an ultrasound is rarely needed. Checking your thyroid hormones (TSH, FT3, FT4) once a year is enough.

If you have had a lobectomy or partial thyroidectomy, it is wise to check the remaining lobe or tissue by ultrasound, because nodules often develop.

If your weight changes, if new medicines such as coumarin anticoagulants (Sintrom) or anti-epileptics are added, or if you have gastritis, have your thyroid checked sooner, as your thyroxine dose may need adjusting.

The usual causes of hyperthyroidism are autoimmune hyperthyroidism and hot nodules, which overproduce thyroxine.

In these forms you should avoid iodised salt, fish and shellfish, and contact with iodine (Betadine, iodinated contrast agents, kelp). It is also best to avoid long periods with your skin in seawater.

A pregnant woman needs to be very well controlled, because for the first 10 weeks the baby has no thyroid of its own and relies on the mother’s thyroxine. This is when the central nervous system develops, and low hormone levels in the mother can affect the child.

A pregnant woman with hypothyroidism should be checked every 2–2½ months and have her thyroxine dose adjusted, because her needs increase — due to weight gain and increased excretion by the kidneys.