Thyroid Gland Introduction
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Questions and Answers

What is the molecular weight of thyroglobulin?

  • 1320 kDa
  • 990 kDa
  • 660 kDa (correct)
  • 330 kDa

    • What percentage of thyroglobulin is made up of carbohydrates by weight?

  • 20%
  • 10% (correct)
  • 15%
  • 5%

    • How many tyrosine residues are normally incorporated into thyroid hormones?

  • 1-2
  • 10-12
  • 15-20
  • 4-8 (correct)

    • What is the name of the enzyme that mediates the oxidation and reaction of iodide with thyroglobulin?

    <p>Thyroid peroxidase</p> Signup and view all the answers

    What happens to the colloid when there is a need for thyroid hormone secretion?

    <p>It is internalized by the thyrocytes by endocytosis</p> Signup and view all the answers

    What is the product formed when two DIT molecules undergo an oxidative condensation?

    <p>T4</p> Signup and view all the answers

    What is the approximate percentage of iodinated compounds in the normal human thyroid that is T3?

    <p>7%</p> Signup and view all the answers

    What is the main difference between the two theories of thyroglobulin coupling?

    <p>One theory involves intramolecular coupling while the other involves intermolecular coupling.</p> Signup and view all the answers

    What is the approximate amount of T4 secreted by the human thyroid per day?

    <p>80 μg (103 nmol)</p> Signup and view all the answers

    What is the function of free thyroid hormones in plasma?

    <p>To inhibit pituitary secretion of TSH.</p> Signup and view all the answers

    What is the name of the protein that binds to thyroid hormones in plasma and tissues?

    <p>All of the above</p> Signup and view all the answers

    What is the approximate normal total plasma T4 level in adults?

    <p>8 μg/dL (103 nmol/L)</p> Signup and view all the answers

    What is the primary function of thyroid hormones in the body?

    <p>To stimulate O2 consumption by most of the cells in the body</p> Signup and view all the answers

    What is the consequence of thyroid gland dysfunction during fetal and neonatal life?

    <p>Mental retardation and dwarfism</p> Signup and view all the answers

    What is the hormone that regulates circulating levels of calcium?

    <p>Calcitonin</p> Signup and view all the answers

    What is the hormone that stimulates the thyroid gland to produce thyroid hormones?

    <p>Thyroid-stimulating hormone (TSH)</p> Signup and view all the answers

    What is the consequence of hypothyroidism in adults?

    <p>Mental and physical slowing and poor resistance to cold</p> Signup and view all the answers

    What is the negative feedback control mechanism that regulates thyroid hormone production?

    <p>High circulating levels of thyroid hormones acting on the hypothalamus and the anterior pituitary</p> Signup and view all the answers

    Which protein has the largest capacity to bind T4?

    <p>Albumin</p> Signup and view all the answers

    What percentage of circulating T4 is normally converted to T3 in adult humans?

    <p>45%</p> Signup and view all the answers

    What is the half-life of transthyretin?

    <p>2 days</p> Signup and view all the answers

    What is the role of deiodination reactions in the liver, kidneys, and other tissues?

    <p>To catabolize and provide a local supply of T3</p> Signup and view all the answers

    What is the primary mediator of the physiologic effects of thyroid secretion?

    <p>T3</p> Signup and view all the answers

    What inhibits TSH secretion in a negative feedback manner?

    <p>Circulating free T4 and T3</p> Signup and view all the answers

    What happens to iodide binding after the injection of TSH?

    <p>It increases within minutes</p> Signup and view all the answers

    What is the effect of thyroid hormones on oxygen consumption?

    <p>It stimulates oxygen consumption</p> Signup and view all the answers

    What is the result of prolonged TSH stimulation on the thyroid gland?

    <p>The gland becomes detectably enlarged</p> Signup and view all the answers

    How do thyroid hormones regulate lipid metabolism?

    <p>By regulating lipid metabolism</p> Signup and view all the answers

    What happens to the expression of genes when thyroid hormones bind to TR in the nuclei?

    <p>Gene expression is increased</p> Signup and view all the answers

    What is the effect of thyroid hormones on the absorption of carbohydrates from the intestine?

    <p>They increase the absorption of carbohydrates</p> Signup and view all the answers

    What is the approximate distribution of DIT in the normal human thyroid?

    <p>33%</p> Signup and view all the answers

    Which of the following proteins has the smallest capacity to bind T4?

    <p>Albumin</p> Signup and view all the answers

    What is the product formed when MIT condenses with DIT?

    <p>T3</p> Signup and view all the answers

    What is the primary mechanism by which TBG binds to T4?

    <p>High-affinity binding</p> Signup and view all the answers

    What is the approximate amount of T3 secreted by the human thyroid per day?

    <p>4 μg (7 nmol)</p> Signup and view all the answers

    What percentage of circulating T4 is converted to RT3?

    <p>45%</p> Signup and view all the answers

    What is the primary function of free thyroid hormones in plasma?

    <p>To inhibit pituitary secretion of TSH</p> Signup and view all the answers

    Which hormone inhibits TSH secretion in a negative feedback manner?

    <p>Free T4 and T3</p> Signup and view all the answers

    What is the result of the coupling of two DIT molecules?

    <p>Formation of T4</p> Signup and view all the answers

    What is the main purpose of deiodination reactions in the liver, kidneys, and other tissues?

    <p>To catabolize thyroid hormones and provide a local supply of T3</p> Signup and view all the answers

    What is the half-life of albumin?

    <p>13 days</p> Signup and view all the answers

    What is the approximate weight percentage of carbohydrate in thyroglobulin?

    <p>10%</p> Signup and view all the answers

    What is the percentage of circulating T3 that is secreted by the thyroid?

    <p>13%</p> Signup and view all the answers

    How many tyrosine residues are normally incorporated into thyroid hormones?

    <p>4–8</p> Signup and view all the answers

    What is the function of thyroid peroxidase in thyroid hormone synthesis?

    <p>To generate reactive iodine species that can attack thyroglobulin</p> Signup and view all the answers

    What happens to the colloid when there is a need for thyroid hormone secretion?

    <p>It is internalized by the thyrocytes and directed toward lysosomal degradation</p> Signup and view all the answers

    What is the product formed when two DIT molecules undergo an oxidative condensation?

    <p>T4</p> Signup and view all the answers

    What is the molecular weight of thyroglobulin?

    <p>660 kDa</p> Signup and view all the answers

    What is the primary function of thyroid hormones in maintaining optimal metabolism?

    <p>Influencing mentation and body mass</p> Signup and view all the answers

    What is the consequence of thyroid gland dysfunction during fetal and neonatal life?

    <p>Mental retardation and dwarfism</p> Signup and view all the answers

    What stimulates the thyroid gland to produce thyroid hormones?

    <p>Thyroid-stimulating hormone (TSH)</p> Signup and view all the answers

    What is the effect of hypothyroidism in adults?

    <p>Mental slowing and physical slowing</p> Signup and view all the answers

    What is the function of calcitonin?

    <p>Regulating circulating levels of calcium</p> Signup and view all the answers

    What controls the secretion of thyroid-stimulating hormone (TSH)?

    <p>Thyroid hormones</p> Signup and view all the answers

    What is the effect of TSH on thyroid function?

    <p>It increases iodide binding, synthesis of T3, T4, and iodotyrosines, and secretion of thyroglobulin into the colloid</p> Signup and view all the answers

    What is the effect of thyroid hormones on lipid metabolism?

    <p>They increase lipid metabolism</p> Signup and view all the answers

    What is the mechanism of action of thyroid hormones?

    <p>They enter cells and bind to receptors in the nuclei</p> Signup and view all the answers

    What is the effect of thyroid hormones on oxygen consumption?

    <p>They increase oxygen consumption</p> Signup and view all the answers

    What is the consequence of prolonged TSH stimulation on the thyroid gland?

    <p>The thyroid gland becomes detectably enlarged</p> Signup and view all the answers

    What is the effect of thyroid hormones on the dissociation of oxygen from hemoglobin?

    <p>They increase the dissociation of oxygen from hemoglobin</p> Signup and view all the answers

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