Thyroid Hormones

The video explores the biosynthesis of thyroid hormones, focusing on T3 (triiodothyronine) and T4 (tetraiodothyronine). It explains the role of thyroglobulin and the iodination process, detailing the activation of iodide and the mechanism of iodination of tyrosine residues. The video also covers the radical mechanism involved in synthesizing T3 and T4, and discusses the function of thyroxine in regulating metabolic rate. Additionally, it touches on hypothyroidism and the use of levothyroxine as a treatment.

What do T3 and T4 stand for in the context of thyroid hormones?

• Triiodothyronine and Tetrahydrothyronine

• Triiodothyronine and Tetraiodine

• Triiodothyronine and Tetraethylene

• Triiodothyronine and Tetraiodothyronine

What is the role of thyroglobulin in thyroid hormone biosynthesis?

• It acts as a catalyst for hormone synthesis.

• It provides the tyrosine residues for iodination.

• It converts T4 to T3.

• It transports hormones in the bloodstream.

Which enzyme is responsible for the iodination of tyrosine residues in thyroglobulin?

• Iodine synthase

• Thyroxine reductase

• Thyroglobulinase

• Thyroid peroxidase

What is hypoiodite in the context of thyroid hormone synthesis?

• A monatomic iodine ion

• An iodide ion with one oxygen atom

• A form of iodine with two oxygen atoms

• A diatomic iodine molecule

What type of reaction is involved in the iodination of tyrosine residues?

• Radical substitution

• Electrophilic aromatic substitution

• Hydrogenation

• Nucleophilic substitution

How are T3 and T4 hormones released from thyroglobulin?

• Through a radical coupling mechanism

• By direct diffusion into the bloodstream

• Via proteolytic cleavage by proteases

• Through passive transport

What is the primary function of T3 in the body?

• To regulate calcium levels

• To store energy

• To decrease metabolic rate

• To increase metabolic rate

What is the role of deiodinases in thyroid hormone regulation?

• They inhibit the synthesis of thyroid hormones.

• They transport thyroid hormones in the blood.

• They convert T4 to the more active T3.

• They synthesize T4 from T3.

What is the medical significance of levothyroxine?

• It inhibits thyroid hormone production.

• It is used to treat hypothyroidism.

• It is a synthetic form of T3.

• It is used to treat hyperthyroidism.

What happens to metabolic rate when thyroid hormone levels are low?

• It fluctuates unpredictably.

• It increases significantly.

• It remains unchanged.

• It decreases.