Causes of Hypothyroidism and Congenital Hypothyroidism
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Questions and Answers

What regulates circulating levels of calcium?

  • Calcitonin (correct)
  • Thyroid peroxidase
  • Thyroglobulin
  • Thyrotropin releasing hormone

    • Which enzyme is responsible for the oxidation and reaction of iodide in the thyroid gland?

  • Thyrotropin releasing hormone
  • Thyroglobulin
  • Thyroxine
  • Thyroid peroxidase (correct)

    • What is the function of thyrotropin releasing hormone (TRH) on thyroid hormone secretion?

  • Stimulates thyroid hormone secretion (correct)
  • Triggers negative feedback control
  • Inhibits thyroid hormone secretion
  • Enhances calcitonin production

    • What is the role of high circulating levels of thyroid hormones in the feedback control mechanism?

    <p>Control thyroid hormone secretion</p> Signup and view all the answers

    What is the primary protein that most of the circulating T4 binds to?

    <p>Thyroxine-binding globulin (TBG)</p> Signup and view all the answers

    Which protein has the shortest half-life among TBG, transthyretin, and albumin?

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

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

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

    Which organ does not play a role in deiodinating T4 and T3?

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

    What is a cause of congenital hypothyroidism according to the text?

    <p>Maternal antithyroid antibodies</p> Signup and view all the answers

    How do drugs inhibit thyroid function according to the text?

    <p>By blocking iodide-trapping mechanism</p> Signup and view all the answers

    What happens when dietary iodine intake falls below 50 μg/day according to the text?

    <p>The thyroid hypertrophies</p> Signup and view all the answers

    How are hypothyroidism and goiter related according to the text?

    <p>Hypothyroidism leads to goiter</p> Signup and view all the answers

    Which of the following compounds inhibit the iodination of monoiodotyrosine and block the coupling reaction in hyperthyroidism?

    <p>Propylthiouracil and methimazole</p> Signup and view all the answers

    Which medication inhibits the conversion of T4 to T3 in many extrathyroidal tissues?

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

    What is the primary cause of hyperthyroidism in Hashimoto thyroiditis during the early stage?

    <p>Excess thyroid hormone secretion</p> Signup and view all the answers

    How does radioactive iodine help in treating severe cases of hyperthyroidism?

    <p>It accumulates in the gland and partially destroys it</p> Signup and view all the answers

    What is the function of calcitonin secreted by the thyroid gland?

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

    How is thyroglobulin synthesized and secreted in the thyroid gland?

    <p>Exocytosis of granules</p> Signup and view all the answers

    What enzyme mediates the oxidation and reaction of iodide with thyroglobulin in the thyroid gland?

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

    How long can humans go without dietary iodide before a decline in circulating thyroid hormone levels is observed?

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

    Which plasma protein has the smallest capacity to bind T4 among albumin, transthyretin, and TBG?

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

    What is the approximate daily secretion of T3 by the human thyroid?

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

    In normal adult humans, what is the approximate plasma T3 level in μg/dL?

    <p>0.15</p> Signup and view all the answers

    Which thyroid hormone is relatively lipophilic and has a larger pool of protein-bound forms in plasma and tissues?

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

    What is the initial product formed during thyroid hormone synthesis?

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

    Which enzyme is responsible for generating reactive iodine species in the thyroid gland?

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

    How is T3 formed in the thyroid gland?

    <p>By condensation of MIT with DIT</p> Signup and view all the answers

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

    <p>3% MIT, 33% DIT, 35% T4, 7% T3</p> Signup and view all the answers

    What is the recommended treatment for iodide deficiency?

    <p>Adding iodized salt to the diet</p> Signup and view all the answers

    Which of the following symptoms is NOT characteristic of hyperthyroidism?

    <p>Cold intolerance</p> Signup and view all the answers

    How does hypothyroidism in the mother affect mental deficiency in offspring?

    <p>Results in more severe mental deficiency in offspring</p> Signup and view all the answers

    What is the primary mechanism for treating congenital hypothyroidism soon after birth?

    <p>Administration of levothyroxine</p> Signup and view all the answers

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