Thyroid Gland
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Questions and Answers

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

  • They all have the same half-life
  • TBG
  • Transthyretin (correct)
  • Albumin

    • What percentage of the circulating T4 is normally converted to RT3?

  • 5%
  • 13%
  • 45% (correct)
  • 87%

    • Which protein binds most of the circulating T4 under physiologic conditions?

  • None of the proteins bind T4 significantly
  • TBG (correct)
  • Albumin
  • Transthyretin

    • What percentage of circulating T3 is secreted by the thyroid gland?

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

    What is the primary function of the thyroid gland?

    <p>Secreting thyroid hormones to maintain metabolism levels</p> Signup and view all the answers

    What can be a cause of hypothyroidism due to pituitary failure?

    <p>Fetal hypopituitary hypothyroidism</p> Signup and view all the answers

    How does iodine deficiency lead to goiter formation?

    <p>By causing thyroid hypertrophy</p> Signup and view all the answers

    How can hypothyroidism in adults be characterized?

    <p>Poor resistance to cold and slowed mental and physical functions</p> Signup and view all the answers

    Which condition can drugs cause by interfering with the iodide-trapping mechanism?

    <p>Thyroid hormone synthesis</p> Signup and view all the answers

    What are the consequences of thyroid gland dysfunction during fetal and neonatal life?

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

    What substance can paradoxically inhibit thyroid function under certain conditions?

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

    How is thyroid function regulated?

    <p>Via thyroid-stimulating hormone (TSH) from the anterior pituitary</p> Signup and view all the answers

    What is the name of the mild and transient inhibition of hormone synthesis produced by large doses of iodide on the thyroid?

    <p>Wolff-Chaikoff effect</p> Signup and view all the answers

    What are individuals called who are hypothyroid from birth or before?

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

    What happens to plasma cholesterol levels in completely athyreotic adults?

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

    What is one of the most common causes of preventable mental retardation worldwide?

    <p>Congenital hypothyroidism</p> Signup and view all the answers

    What is the main reason why thyroid hormones need to enter cells?

    <p>To increase metabolic rate</p> Signup and view all the answers

    Which disorder is characterized by body wasting, nervousness, and tachycardia due to an overactive thyroid gland?

    <p>Graves disease</p> Signup and view all the answers

    What critical roles do thyroid hormones play in development, especially related to the nervous system?

    <p>Aiding in normal mentation</p> Signup and view all the answers

    What can be done to address iodide deficiency as mentioned in the text?

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

    What is a characteristic symptom of hyperthyroidism according to the text?

    <p>Fine tremor of the outstretched fingers</p> Signup and view all the answers

    How can congenital hypothyroidism be treated shortly after birth?

    <p>Levothyroxine administration</p> Signup and view all the answers

    What are the primary functions of the thyroid gland?

    <p>Regulate metabolism and influence body mass and mentation</p> Signup and view all the answers

    What is the recommended way to assess thyroid function according to the text?

    <p>Uptake of tracer doses of radioactive iodine</p> Signup and view all the answers

    What are the consequences of thyroid dysfunction during fetal and neonatal life?

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

    How does excess thyroid secretion affect the body?

    <p>Results in nervousness, tachycardia, tremor, and excess heat production</p> Signup and view all the answers

    What controls thyroid function in the body?

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

    What symptoms are commonly observed in completely athyreotic adults?

    <p>Coarse and sparse hair, dry and yellowish skin, intolerance to cold, slow mentation</p> Signup and view all the answers

    What are the consequences of congenital hypothyroidism in children?

    <p>Dwarfism and mental retardation</p> Signup and view all the answers

    How does maternal antithyroid antibodies affect fetal thyroid function?

    <p>Cross the placenta and damage the fetal thyroid</p> Signup and view all the answers

    What is the potential outcome for children with congenital hypothyroidism if treatment is initiated promptly after birth?

    <p>Normal growth and development with avoidance of mental retardation</p> Signup and view all the answers

    What is the first product generated in the thyroid hormone synthesis process?

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

    Which enzyme is responsible for generating reactive iodine species that attack thyroglobulin?

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

    In the normal human thyroid, what is the average distribution of iodinated compounds for T4?

    <p>35%</p> Signup and view all the answers

    How is T3 formed in the thyroid gland?

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

    What is the role of calcitonin in thyroid gland function?

    <p>Regulates circulating levels of thyroid hormones</p> Signup and view all the answers

    How does the thyroid gland respond to high circulating levels of thyroid hormones?

    <p>Undergoes negative feedback control</p> Signup and view all the answers

    Which enzyme is responsible for mediating the oxidation and iodide reaction in thyroglobulin?

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

    What is the molecular weight of thyroglobulin and its carbohydrate composition?

    <p>$660 kDa, 10% carbohydrate by weight</p> Signup and view all the answers

    What happens to the thyroid gland when TSH stimulation is prolonged?

    <p>It undergoes hypertrophy.</p> Signup and view all the answers

    What is the main cause of an enlarged thyroid gland known as a goiter?

    <p>Overstimulation by TSH</p> Signup and view all the answers

    What characterizes the syndrome of adult hypothyroidism, often referred to as myxedema?

    <p>Skin changes</p> Signup and view all the answers

    What is the immediate effect after the administration of TSH in terms of thyroid activity?

    <p>Enhanced synthesis of T3 and T4</p> Signup and view all the answers

    What is the primary mechanism by which thyroid hormones exert their effects within cells?

    <p>Interacting directly with DNA</p> Signup and view all the answers

    Which of the following best describes the consequences of hypothyroidism in neonatal life?

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

    In the context of thyroid gland dysfunction, what is the primary difference between hypothyroidism and overactivity of the thyroid gland?

    <p>Hypothyroidism involves a reduction in secretion of TSH, while overactivity is triggered by autoantibodies.</p> Signup and view all the answers

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