Question

Write short note on the function of Thyroid hormones.

Answer 1

Thyroid hormones are two hormonesproduced and released by the thyroid gland, namely triiodothyronine (T3) and thyroxine(T4). They are tyrosine-based hormones that are primarily responsible for regulation ofmetabolism. T3 and T4 are partially composed of iodine. A deficiency of iodine leads to decreased production of T3 and T4, enlarges the thyroid tissue and will cause the disease known as simple goitre. The major form of thyroid hormone in the blood is thyroxine (T4), which has a longer half-life than T3.[1] In humans, the ratio of T4 to T3 released into the blood is approximately 14:1[2]. T4 is converted to the active T3 (three to four times more potent than T4) within cells by deiodinases (5'-iodinase). These are further processed bydecarboxylation and deiodination to produceiodothyronamine (T1a) and thyronamine(T0a). All three isoforms of the deiodinases are selenium-containing enzymes, thus dietary selenium is essential for T3production. Edward Calvin Kendall was responsible for the isolation of thyroxine in 1915.[3]

Answer 2

Dear Student,

◆ Thyroid hormones -

There are three hormones secreted by thyroid -

1. Triiodothyronine (T3)
2. Thyroxine (T4)
3. Calcitonin

# Functions of thyroid hormones -

1. Increases metabolic rate
2. Growth and development of bone, soft tissues
3. Increases sensitivity to catecholamines
4. Stimulates heart rate and contractility
5. Stimulate protein and fat synthesis
6. Maintains electrolyte balance
7. Helps in red cell formation

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