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Hormones, 6 steps, about 4 minutes

Thyroid basics

How a small gland in your neck sets your metabolic pace, and how thyroid problems are diagnosed.

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The steps

  1. The pace setter

    The thyroid makes hormones that regulate metabolism, including growth and how much energy the body uses.

    Thyroid gland

    Source: Better Health Channel (Victorian Government), Thyroid gland

  2. Built from iodine

    The thyroid needs iodine to make its hormones. Since 2009, manufactured bread in Australia has been made with iodised salt.

    Iodine

    Sources: Better Health Channel (Victorian Government), Thyroid gland; healthdirect Australia, Foods high in iodine

  3. T4 and T3

    The thyroid makes mostly T4. T3 is more active but made in smaller amounts, and the pituitary gland sets the pace with TSH.

    Thyroid hormone production

    Source: Better Health Channel (Victorian Government), Thyroid gland

  4. The most common cause of an underactive thyroid

    In Australia, the most common cause of an underactive thyroid is Hashimoto's disease, in which the immune system attacks the thyroid gland.

    Hashimoto's disease

    Sources: healthdirect Australia, Hypothyroidism (underactive thyroid); healthdirect Australia, Hashimoto's disease

  5. When the pace slows

    Tiredness, weight gain, feeling cold, constipation and low mood can follow. Thyroid hormone replacement treats it and is usually lifelong.

    Hypothyroidism (underactive thyroid)

    Source: healthdirect Australia, Hypothyroidism (underactive thyroid)

  6. How it is checked

    TSH is measured first. If it is abnormal, free T4 and sometimes free T3 are added.

    Thyroid function tests (TSH, free T4, free T3)

    Source: Pathology Tests Explained, Thyroid function tests

Quiz

1. What mineral does the thyroid need to make its hormones?

Answer: Iodine. Iodine is essential for the production of thyroid hormones.

Source: Better Health Channel (Victorian Government), Thyroid gland

2. What is the most common cause of an underactive thyroid in Australia?

Answer: Hashimoto's disease. healthdirect identifies Hashimoto's disease, an autoimmune condition, as the most common cause of hypothyroidism in Australia.

Source: healthdirect Australia, Hypothyroidism (underactive thyroid)

3. What happens to TSH when thyroid hormone is low?

Answer: It rises. When thyroid hormone is low, the pituitary makes more TSH, and when it is high, it makes less.

Source: Better Health Channel (Victorian Government), Thyroid gland

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