5.3

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Which of the following best describes the mechanism of thyroid hormone action?

Inhibiting gene transcription to regulate metabolism

Increasing protein synthesis to stimulate cellular metabolism (correct)

Binding to surface receptors to stimulate adenylate cyclase

Stimulating the release of neurotransmitters to regulate appetite

What is the primary function of the hypothalamus in regulating thyroid function?

To regulate the release of thyroid hormones from the thyroid gland

To stimulate the synthesis of thyroglobulin

To secrete thyroid-stimulating hormone (TSH)

To produce thyrotropin-releasing hormone (TRH) to stimulate the pituitary (correct)

Which of the following are results of hyperthyroidism?

Increased appetite and weight loss (correct)

Decreased protein synthesis and muscle atrophy

Increased synthesis of thyroid hormones and weight gain

Decreased metabolic rate and weight gain

What is the primary function of the pituitary in regulating thyroid function?

To release thyroid-stimulating hormone (TSH) to stimulate the thyroid gland Signup and view all the answers

Approximately, what is the percentage of T4 and T3 that is bound to plasma proteins?

99% Signup and view all the answers

What is the result of the outer ring deiodination of T4?

Conversion of T4 to T3 Signup and view all the answers

What is the primary function of thyroid hormone T3?

Regulation of metabolic rate and heat production Signup and view all the answers

What is the result of the hydrolysis of thyroglobulin in lysosomal pathway?

Production of free T4 and T3 and iodinated residues Signup and view all the answers

What is the function of thyroid-binding globulin?

To provide a reservoir of hormones with a longer half-life Signup and view all the answers

What is the primary mechanism of action of T3 in the nucleus?

It combines with a nuclear receptor to stimulate transcription of genes for the production of mRNAs Signup and view all the answers

What is the percentage of T3 and T4 that binds to thyroid-binding globulin (TBG) or transthyretin (TTR) in the plasma?

More than 99.5% Signup and view all the answers

What is the mechanism by which T4 is converted to T3 in the cytosol?

Deiodination Signup and view all the answers

What is the percentage of T3 that is released from the thyroid gland?

Around 2-3% Signup and view all the answers

What is the name of the protein that T3 and T4 bind to in the plasma?

Thyroid-binding globulin (TBG) and transthyretin (TTR) Signup and view all the answers

What is the effect of excess TSH on the thyroid gland?

Hypertrophy of the thyroid gland Signup and view all the answers

What is the most common form of hyperthyroidism?

Graves' disease Signup and view all the answers

What is the diagnosis of hyperthyroidism based on?

Low TSH and high T3 and T4 Signup and view all the answers

What is the anesthetic concern in hyperthyroidism?

Thyroid storm Signup and view all the answers

What is the preoperative management of hyperthyroidism in emergency surgery?

Propylthiouracil (PTU) and beta blocker Signup and view all the answers

What is the potential complication of goiter during thyroid surgery?

Tracheal deviation Signup and view all the answers

Which of the following is not essential for normal biosynthesis of thyroid hormones?

Ferritin Signup and view all the answers

What is the effect of an increase in plasma levels of TSH alone have on metabolic rate?

It has no effect on the metabolic rate Signup and view all the answers

In which condition is the TSH response to TRH most likely to be reduced?

Hyperthyroidism due to diffuse hyperplasia of thyrotropes Signup and view all the answers

What is the effect of TSH injections on thyroidal uptake of iodine?

It increases the uptake of iodine Signup and view all the answers

Which of the following hormones is least affected by an increase in plasma levels of TRH?

TBG Signup and view all the answers

5.3

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