Thyroid Gland Overview and Hormones
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Questions and Answers

What is the first-line treatment for hypothyroidism?

  • Propylthiouracil
  • Liothyronine sodium (T3)
  • Carbimazole
  • Levothyroxine sodium (T4) (correct)
  • What autoimmune disease is commonly associated with hyperthyroidism?

  • Thyroid toxic adenoma
  • Hashimoto's disease
  • Cushing's syndrome
  • Graves' disease (correct)
  • Which of the following symptoms is NOT typically associated with hyperthyroidism?

  • Cold intolerance (correct)
  • Weight loss
  • Tremors in fingers
  • Increased heart rate
  • Which treatment aims to block the conversion of T4 to T3 in hyperthyroidism?

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

    What level decreases in the blood due to hyperthyroidism?

    <p>Thyroid Stimulating Hormone (TSH)</p> Signup and view all the answers

    What is the primary function of the follicular cells in the thyroid gland?

    <p>Trap iodide</p> Signup and view all the answers

    What are the two main hormones produced by the thyroid gland?

    <p>Thyroxine and triiodothyronine</p> Signup and view all the answers

    Which process involves the iodination of tyrosine residues in the thyroid?

    <p>Iodination of tyrosyl residues by thyroperoxidase</p> Signup and view all the answers

    How does the thyroid gland concentrate iodine?

    <p>By using Na+/I- symporter and I-/Cl- porter</p> Signup and view all the answers

    What structural change occurs in acinar cells during hyperactivity of the thyroid gland?

    <p>Cells become tall and columnar</p> Signup and view all the answers

    What is formed when monoiodotyrosine (MIT) couples with diiodotyrosine (DIT)?

    <p>Triiodothyronine (T3)</p> Signup and view all the answers

    Which condition describes the structural appearance of inactive acinar cells?

    <p>Thin and flattened</p> Signup and view all the answers

    What role do parafollicular cells have in the thyroid gland?

    <p>Release calcitonin</p> Signup and view all the answers

    Which thyroid hormone is considered more active and has a faster effect?

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

    What is the primary source of T3 in the body?

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

    What is the duration of the half-life of T4 in the blood?

    <p>6 days</p> Signup and view all the answers

    Which of the following is a common symptom of hypothyroidism?

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

    What happens to the thyroid gland in response to iodine deficiency?

    <p>It swells</p> Signup and view all the answers

    In the condition known as cretinism, what is the likely cause?

    <p>Genetic defect</p> Signup and view all the answers

    How does T3 affect protein synthesis in cells?

    <p>Turns it on</p> Signup and view all the answers

    What is a distinguishing feature of Hashimoto's thyroiditis?

    <p>Autoimmune attack on thyroid cells</p> Signup and view all the answers

    What is the consequence of untreated congenital hypothyroidism?

    <p>Severe brain damage</p> Signup and view all the answers

    Which thyroid hormone is bound more in the blood?

    <p>T4 has higher binding</p> Signup and view all the answers

    Which hormones are predominantly secreted by the thyroid gland?

    <p>80-90% T4, 10-20% T3</p> Signup and view all the answers

    What is the major function of Thyrotropin-releasing hormone (TRH) in thyroid hormone regulation?

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

    What role does calcitonin play in the body?

    <p>Responsible for building of bone</p> Signup and view all the answers

    Which of the following is NOT a general effect of thyroid hormones?

    <p>Stimulate gluconeogenesis</p> Signup and view all the answers

    What mechanism regulates the secretion of TSH?

    <p>Negative feedback from elevated T3</p> Signup and view all the answers

    Which type of cells is responsible for the uptake and digestion of colloid in the thyroid?

    <p>Follicle cells</p> Signup and view all the answers

    Which of the following actions is primarily attributed to thyroid hormones?

    <p>Increased uptake from the gastrointestinal tract</p> Signup and view all the answers

    What percentage of circulating T4 and T3 is free and unbound in the bloodstream?

    <p>0.03% T4 and 0.3% T3</p> Signup and view all the answers

    Which of the following hormones primarily binds to thyroxine-binding globulin in circulation?

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

    What is the main site of action for thyroid hormones in the body?

    <p>Cell nucleus</p> Signup and view all the answers

    Study Notes

    Thyroid Gland Overview

    • The thyroid gland is a large endocrine gland, weighing 18-60g in adults.
    • Its location is caudal to the larynx, adhering to the front of the trachea.
    • It's shaped like a shield (Greek: "shield-like").
    • The gland concentrates iodine from the blood stream.
    • It's composed of two lobes connected by an isthmus.

    Thyroid Hormone Production

    • Follicular cells produce thyroid hormones (T3 and T4).
    • Follicular cells trap iodine actively against a concentration gradient, using Na+/I- symporters.
    • Thyroglobulin (TGB) is produced and stored in the colloid.
    • Tyrosine in TGB is iodinated to form MIT and DIT.
    • MIT and DIT couple to form T3 and T4.
    • Thyroid hormones are released into the blood.
    • T4 is largely a prohormone and is converted to T3 outside the thyroid.

    Thyroid Hormone Regulation

    • The hypothalamus produces TRH.
    • TRH stimulates the anterior pituitary to release TSH.
    • TSH stimulates the thyroid gland to produce more hormones.
    • High T3 and T4 levels inhibit TRH and TSH release.

    Actions of Thyroid Hormones

    • T3 andT4 increase the metabolic rate.
    • They enhance protein synthesis, breakdown of fats, and glucose usage in ATP production.
    • They affect nervous system maturation during fetal development and modulate heart rate.
    • Calcitonin, produced by C-cells, regulates bone building.

    Thyroid Diseases

    • Hypothyroidism: Reduced hormone production. Symptoms include slow metabolic rate, weight gain, fatigue, and cold intolerance. It can be treated with T4 replacement therapy. Causes include iodine deficiency, autoimmune (Hashimoto's) attack, or congenital defects.
    • Hyperthyroidism: Excess hormone production. Symptoms include elevated metabolic rate, weight loss, anxiety, heat intolerance, and rapid heart rate. It can be treated using antithyroid medications, radioactive iodine, or surgery. Common causes are Graves' disease (autoimmune) or toxic nodules.
    • Goiter: Enlarged thyroid gland, often a symptom of iodine deficiency.
    • Thyroid nodules: Growths often benign and cause either over or underactive thyroid function.

    Importance of Thyroid Hormones

    • Thyroid hormones are vital for normal growth and development throughout life.
    • They are essential for many body tissues and have actions at the cellular level (especially in the nucleus).
    • Basal metabolic rate (BMR) is increased by thyroid hormones in adults.

    Thyroid Hormone Properties

    • Most thyroid hormone is secreted as T4 (80 µg/day). T3 is more active with a much faster rate of turnover and better receptor binding.

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    Related Documents

    Lect 13 Thyroid PDF

    Description

    This quiz covers the anatomy and physiology of the thyroid gland, including its structure, hormone production, and regulatory mechanisms. Test your knowledge on key concepts such as T3 and T4 synthesis, and the roles of TRH and TSH in hormone regulation.

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