Question

Thyroxine ________ BMR.
A.Increases
B.Decreases
C.Uncertain
D.No effect

Answer 1

Triiodothyronine (T3) and thyroxine (T4) are two main thyroid glands produced by the thyroid gland. These are primarily responsible for the regulation of metabolism that is tyrosine-based hormones. Iodine is present partially in T3 and T4. A deficiency of iodine leads to decreased production of T3 and T4, enlarges the thyroid tissue, and causes a simple goiter. Thyroxine (T4) is the major type of hormone present in the bloodstream which has a longer half-life than T3.

Complete answer: The main function of the thyroid is the production of the iodine-containing thyroid hormones, triiodothyronine (T3) and thyroxine (T4), and the peptide hormone calcitonin. The thyroid hormones are created from iodine and tyrosine. Thyroid hormones influence the appetite, absorption of substances, and gut motility. Absorption in the gut is increased, generation, uptake by cells, and breakdown of glucose are the portal functions performed by the thyroid gland. Breakdown of fats and an increase in the number of free fatty acids are stimulated by these thyroid hormones. With increasing the free fatty acids, thyroid hormones decrease cholesterol levels, perhaps by increasing the rate of secretion of cholesterol in the bile of the liver in the body. Most of the thyroid diseases are due to the thyroid gland and most of them are autoimmune that is caused by releasing the auto bodies from their own body.
Hence, the correct option is (A) Increases.

Note: The thyroid hormones are synthesized from thyroglobulin. This is a protein within the colloid in the follicular lumen that is synthesized within the rough endoplasmic reticulum of follicular cells and then transported into the follicular lumen. Thyroid-stimulating hormone (TSH), released by the anterior pituitary gland regulates the production of thyroid hormones. Thyrotropin-releasing hormone (TRH) stimulates the thyrotropin that is released from the hypothalamus in a pulsatile manner.