Thyroid (Physiology)

Which of the following best describes the histological structure of the thyroid gland?

• It is composed of multiple follicles surrounded by multiple layers of polarized epithelial cells.

• It contains follicles filled with proteinaceous material called colloid and surrounded by a single layer of polarized epithelial cells.

• It consists mainly of dense connective tissue with scattered thyroid cells.

• It has a structure predominantly composed of loose connective tissue with no specific follicular organization.

What is the most important early effect of Thyrotrophin (TSH) on the thyroid gland?

• Decreased activity of the iodide pump

• Decreased iodination of tyrosine to form thyroid hormones

• Decreased proteolysis of thyroglobulin

• Increased proteolysis of thyroglobulin

Which plasma protein has the highest capacity to bind T4 before becoming saturated?

• Transthyretin

• Albumin

• Thyroxine-binding globulin (TBG)

• Hemoglobin

In the context of thyroid hormone regulation, what is the role of thyroid-stimulating immunoglobulins (TSI)?

• They mimic the action of TSH and stimulate the thyroid gland to secrete T3 and T4.

• They inhibit the secretion of TSH and thus decrease the production of thyroid hormones.

• They act independently of TSH and suppress thyroid hormone secretion.

• They facilitate the binding of TBG to T3 and T4, decreasing their availability.

What effect do thyroid hormones have on basal metabolic rate (BMR)?

• They decrease BMR due to a decrease in Na-K-ATPase activity.

• They have no significant effect on BMR but influence body temperature regulation.

• They increase BMR primarily by up-regulating expression and increasing activity of the Na-K-ATPase in most tissues.

• They increase BMR by directly stimulating mitochondrial DNA replication.

What is the primary physiological effect of thyroxine-binding globulin (TBG) on thyroid hormone levels in the blood?

• TBG decreases the overall thyroid hormone levels.

• TBG increases the conversion rate of T4 to T3.

• TBG stabilizes free thyroid hormone levels by binding excess hormones.

• TBG directly stimulates the thyroid gland to produce more hormone.

Which of the following is a direct effect of thyroid hormones on the central nervous system (CNS)?

• Decrease in synaptic transmission speed.

• Promotion of myelination and axonal growth.

• Reduction in cerebral blood flow.

• Inhibition of neurotransmitter release.

What is the role of thyroid-stimulating hormone (TSH) in the synthesis of thyroid hormones?

• It inhibits the synthesis of T3 and T4 to maintain hormone balance.

• It stimulates the uptake of iodine and the production of thyroglobulin.

• It decreases the iodination of tyrosine.

• It promotes the excretion of thyroid hormones from the thyroid gland.

Which condition is characterized by high circulating levels of thyroid hormones due to thyroid-stimulating immunoglobulins?

• Hashimoto’s thyroiditis

• Thyroid storm

• Graves' disease

• Subacute thyroiditis

Which thyroid hormone is primarily responsible for regulating metabolism and is more potent?

• Thyroxine

• Triiodothyronine

• Reverse T3 (rT3)

• Thyroglobulin