What is the role of the thyroid gland within the body?

The thyroid gland is part of the endocrine system. It has an essential role in metabolism as well as growth and development.

Prevalence of hypothyroidism

Hypothyroidism affects 2% of the overall population and 5% of people over 60 years old. It is 5-10 times more common in women. Disease onset usually occurs between 30 and 60 years of age.

Symptoms of hypothyroidism

Hypothyroidism is characterised by a slowing down of body processes. This can produce symptoms such as:

• Fatigue

• Weight gain

• Sensitivity to cold

• Constipation

• Depression

• Muscle pain and weakness

• Muscle cramps

Testing for thyroid disorder

1. Test TSH levels alone for adults when secondary thyroid dysfunction (pituitary disease) isn’t suspected.

2. If TSH is above the reference range, measure FT4 (free thyroxine) in the same sample.

3. If TSH is below the reference range, measure FT4 and FT3 (free tri-iodothyronine) in the same sample.

Treatment

Replacement therapy is the treatment for hypothyroidism. Levothyroxine is a synthetic hormone given as medication to people with hypothyroidism and it mimics the actions of the natural hormone.

Starting dose for an adult is 1.6 micrograms/kg once daily (rounded to the nearest 25 microgram). The dose of levothyroxine is then increased by 25 or 50 micrograms every 3-4 according to the patient’s response. Maintenance dose is between 50-200 micrograms daily.

It is advised that patients take their levothyroxine preferably 30-60 minutes before breakfast, caffeine containing liquids (tea or coffee) as caffeine can reduce the amount of levothyroxine taken in by the body.

Treatment monitoring

The aim of replacement therapy is to maintain TSH (thyroid-stimulating hormone) within reference range. If symptoms persist, consider adjusting the dose. Note: it may take up to 6 months for TSH levels to return to reference range.

Adults should have their TSH measured every 3 months until the level has stabilised (2 similar measurements within the reference range 3 months apart), and then annually.

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