Thyroid Hormones Mechanism of Action
20 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which of the following mechanisms allows Propylthiouracil (PTU) to diminish the effects of hyperthyroidism?

  • Increases gluconeogenesis
  • Promotes the production of T4
  • Inhibits the oxidation of iodide
  • Inhibits 5'-deiodinase to reduce T3 levels (correct)

    • What is a significant contraindication for Methimazole use during pregnancy?

  • It has been associated with teratogenic effects (correct)
  • It can cause weight gain
  • It is not effective for hyperthyroidism
  • It can lead to skin rash

    • What adverse effect is commonly associated with thionamides?

  • Weight loss
  • Hyperkalemia
  • Agranulocytosis (correct)
  • Hypertension

    • Which of the following conditions is treated with synthetic thyroid hormones like Levothyroxine?

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

    What primary action do aldosterone analogues perform in the kidneys?

    <p>Promote sodium reabsorption</p> Signup and view all the answers

    Which side effect is associated with the use of Levothyroxine?

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

    Calcium-sensing receptor agonists like Cinacalcet are primarily used in the management of which condition?

    <p>Secondary hyperparathyroidism in CKD</p> Signup and view all the answers

    Which drug can cause hepatotoxicity as a side effect?

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

    What is a common side effect associated with Fludrocortisone?

    <p>Exacerbation of heart failure</p> Signup and view all the answers

    Which of the following drugs is misused for weight loss?

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

    What is the primary role of Thyroid Peroxidase in the synthesis of thyroid hormones?

    <p>Oxidation and organification of iodide</p> Signup and view all the answers

    What additional mechanism does Propylthiouracil (PTU) utilize beyond inhibiting thyroid hormone synthesis?

    <p>Inhibits 5'-deiodinase enzyme</p> Signup and view all the answers

    Which of the following is a significant side effect of thionamides?

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

    Which adverse effect is most commonly associated with synthetic thyroid hormones like Levothyroxine?

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

    What is NOT a clinical use of Aldosterone analogues like Fludrocortisone?

    <p>Treatment of hyperthyroidism</p> Signup and view all the answers

    What primary effect does aldosterone have on the kidneys?

    <p>Promotes sodium reabsorption</p> Signup and view all the answers

    What condition can Cinacalcet help manage?

    <p>Secondary hyperparathyroidism</p> Signup and view all the answers

    Which is an important contraindication for using Levothyroxine?

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

    What is a significant side effect of aldosterone analogues?

    <p>Fluid retention</p> Signup and view all the answers

    How does aldosterone affect potassium levels in the body?

    <p>Increases potassium excretion</p> Signup and view all the answers

    Study Notes

    Thyroid Hormones

    • Hyperthyroidism can lead to elevated blood sugar levels through increased gluconeogenesis and glycolysis.

    Inhibition of Thyroid Peroxidase

    • Thyroid peroxidase is essential for:
      • Oxidation of iodide.
      • Attachment of iodine to tyrosine (organification) on thyroglobulin.
      • Coupling of iodinated tyrosines to form thyroid hormones.
    • Thionamides inhibit these processes, preventing synthesis of T3 (triiodothyronine) and T4 (thyroxine).

    Propylthiouracil (PTU)

    • PTU inhibits 5'-deiodinase, which converts T4 into the more active T3.
    • By reducing active T3 levels, PTU further diminishes the effects of hyperthyroidism.

    Treatment of Thyroid Disorders

    • Thionamides:

      • Clinical Use: Manage hyperthyroidism; Methimazole for 2nd/3rd trimester; PTU primarily in 1st trimester.
      • Side Effects: Skin rash, agranulocytosis, aplastic anemia, hepatotoxicity.
      • Contraindications: Methimazole in 1st trimester; PTU in 2nd/3rd trimester due to hepatotoxicity.

    • Levothyroxine and Liothyronine:

      • Clinical Use: Treat hypothyroidism, myxedema, weight loss.
      • Side Effects: Tachycardia, heat intolerance, tremor, arrhythmias.
      • Contraindications: Misuse for weight loss, specific drug interactions (antacids, bile acid resins, ferrous sulfate).

    • Aldosterone Analogue:

      • Clinical Use: Mineralocorticoid replacement therapy for primary adrenal insufficiency.
      • Side Effects: Heart failure exacerbation, fluid retention (edema), hyperpigmentation.

    Mechanism of Action of Drugs Affecting Mineralocorticoid Receptors

    • Synthetic aldosterone analogues exhibit both mineralocorticoid and glucocorticoid effects.

    Hyperthyroidism and Glucose Metabolism

    • Hyperthyroidism increases gluconeogenesis and glycolysis, raising blood sugar levels.

    Thionamides Mechanism of Action

    • Inhibit Thyroid Peroxidase, essential for iodine oxidation, organification, and coupling in thyroid hormone synthesis.
    • Propylthiouracil (PTU) also inhibits 5'-deiodinase, blocking conversion of T4 to T3, reducing active T3 levels.

    Thionamides Overview

    • Clinical Uses:
      • Methimazole for pregnancy (2nd/3rd trimester)
      • PTU for pregnancy (1st trimester)
    • Side Effects:
      • Risk of skin rash, agranulocytosis, aplastic anemia, and hepatotoxicity.
      • Methimazole and PTU both teratogenic.
    • Contraindications:
      • Methimazole: avoid in 1st trimester due to teratogenicity.
      • PTU: avoid in 2nd/3rd trimester due to hepatotoxicity.

    Levothyroxine and Liothyronine Overview

    • Clinical Uses:
      • Treatment of hypothyroidism, myxedema, and weight loss management.
    • Side Effects:
      • Can cause tachycardia, heat intolerance, tremors, and arrhythmias.
    • Contraindications:
      • Levothyroxine interacts with antacids, bile acid resins, and ferrous sulfate.
    • Misuse observed for weight loss and diagnostic tests include TSH receptor antibody test and radioactive iodine uptake.

    Aldosterone Analogue Overview

    • Synthetic aldosterone analogue (mineralocorticoid) with glucocorticoid properties.
    • Used for mineralocorticoid replacement in primary adrenal insufficiency.
    • Can exacerbate heart failure, cause fluid retention (edema), and hyperpigmentation.

    Aldosterone Mechanism of Action

    • Acts on distal convoluted tubules and collecting ducts in kidneys by binding to mineralocorticoid receptors.
    • Stimulates sodium-potassium pumps, enhancing sodium reabsorption into blood while promoting potassium and hydrogen ion excretion.
    • Increases blood volume and blood pressure through osmosis as water follows reabsorbed sodium.

    Cinacalcet Overview

    • Clinical uses were not provided; additional information might be needed for detailed context.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Description

    This quiz explores the mechanisms of thyroid hormones, including their role in hyperthyroidism and processes like gluconeogenesis and glycolysis. Additionally, it covers the inhibition of thyroid peroxidase and its effect on the synthesis of T3 and T4 hormones through thionamides.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser