Thyroid Disorders Quiz
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Questions and Answers

What is the primary cause of hyperthyroidism?

  • Excess circulating levels of free thyroxine (T4) or free triiodothyronine (T3) (correct)
  • Overactivity of the parathyroid gland
  • Decreased metabolism leading to weight gain
  • Insufficient production of thyroid hormone by the thyroid gland
  • Which statement describes hypothyroidism?

  • It leads to an accelerated metabolism.
  • It is caused by inadequate production of thyroid hormone. (correct)
  • It results from an excess of thyroid hormones in circulation.
  • It is typically associated with parathyroid hormone imbalance.
  • Which of the following pharmacological treatments is primarily used for hyperthyroidism?

  • Levothyroxine
  • Calcitriol
  • Calcium carbonate
  • Methimazole (correct)
  • What is a common side effect associated with treatments for hypothyroidism?

    <p>Fatigue or lethargy from excess thyroid hormone (B)</p> Signup and view all the answers

    What is a potential outcome of untreated hyperparathyroidism?

    <p>Increased calcium levels leading to kidney stones (C)</p> Signup and view all the answers

    Which condition is characterized as an autoimmune disease affecting the TSH receptor?

    <p>Graves' disease (B)</p> Signup and view all the answers

    What laboratory finding is indicative of hyperthyroidism?

    <p>High Serum T4 (C)</p> Signup and view all the answers

    Which imaging method is primarily used for assessing thyroid uptake in cases of hyperthyroidism?

    <p>Radioactive imaging using Iodine (B)</p> Signup and view all the answers

    What process releases T4, T3, and iodotyrosines during the biosynthesis of thyroid hormones?

    <p>Proteolysis of Tg (A)</p> Signup and view all the answers

    Which of the following conditions is a benign tumor that cannot metastasize?

    <p>Toxic thyroid adenoma (C)</p> Signup and view all the answers

    What is the primary mechanism of action of thio(n)amides?

    <p>Inhibition of thyroperoxidase and 5'-deiodinase (B)</p> Signup and view all the answers

    Which drug has the shortest half-life among the thio(n)amides?

    <p>Propylthiouracil (B)</p> Signup and view all the answers

    What is a key characteristic of carbimazole in relation to methimazole?

    <p>Carbimazole is a pro-drug converted into methimazole (B)</p> Signup and view all the answers

    What is one of the effects of propylthiouracil (PTU) on hormone conversion?

    <p>Decreases T4 to T3 conversion (A)</p> Signup and view all the answers

    What is a common reason for a latent period before clinical improvement with thio(n)amides?

    <p>High levels of stored thyroid hormone (B)</p> Signup and view all the answers

    Which laboratory finding is typically observed in hyperthyroidism?

    <p>High Serum T4 (B)</p> Signup and view all the answers

    What role does iodide trapping play in the biosynthesis of thyroid hormones?

    <p>It facilitates the oxidative iodination of tyrosine. (D)</p> Signup and view all the answers

    Which imaging technique is specifically noted for thyroid uptake scans?

    <p>Radioactive imaging using Iodine (I123) (B)</p> Signup and view all the answers

    Which condition is associated with an overgrowth of the thyroid gland?

    <p>Toxic multinodular goitre (A)</p> Signup and view all the answers

    What is a key characteristic of anti-TSH receptor antibodies in the context of hyperthyroidism?

    <p>They mimic TSH, leading to increased thyroid hormone production. (A)</p> Signup and view all the answers

    What causes the condition known as hyperthyroidism?

    <p>Excess of circulating free thyroxine (T4) or free triiodothyronine (T3) (C)</p> Signup and view all the answers

    Which of the following statements best reflects the pharmacokinetics associated with treatments for hypothyroidism?

    <p>They have a prolonged half-life allowing for extended dosing intervals (A)</p> Signup and view all the answers

    What is a common side effect associated with the pharmacological treatment of hyperparathyroidism?

    <p>Hypercalcemia leading to confusion (D)</p> Signup and view all the answers

    What characterizes the mechanism of action of the drugs used for treating hyperthyroidism?

    <p>Decreased synthesis of thyroid hormones (A)</p> Signup and view all the answers

    In the context of parathyroid treatment, what is the rationale for using pharmacological agents?

    <p>To inhibit the action of PTH on bone metabolism (B)</p> Signup and view all the answers

    What is the primary mechanism by which thio(n)amides reduce thyroid hormone levels?

    <p>Inhibition of thyroperoxidase (TPO) (D)</p> Signup and view all the answers

    Which thio(n)amide specifically inhibits the 5'-deiodinase enzyme responsible for converting T4 to T3?

    <p>Propylthiouracil (PTU) (A)</p> Signup and view all the answers

    What is a notable pharmacokinetic difference between propylthiouracil (PTU) and methimazole?

    <p>Methimazole has a half-life of about 4-6 hours, whereas PTU's is 1 hour (A)</p> Signup and view all the answers

    How quickly can thio(n)amides lead to significant inhibition of iodine utilization in the thyroid gland?

    <p>Within 12 hours for 90% inhibition (A)</p> Signup and view all the answers

    What factor contributes to the latent period before clinical improvement when using thio(n)amides?

    <p>Large storage of thyroid hormone in the body (D)</p> Signup and view all the answers

    Study Notes

    Thyroid Gland

    • The thyroid gland controls metabolism in the body.
    • Hyperthyroidism is high thyroid hormone in the blood, increasing the speed of body processes.
    • Treatment options for hyperthyroidism include radioactive iodine, surgery, and thioureylenes.
    • Patients on antithyroid drugs should be counselled about agranulocytosis.
    • Beta-blockers may be used to manage excess thyroid hormone.
    • Hypothyroidism is low thyroid hormone, slowing down body processes.
    • Treatment for hypothyroidism is levothyroxine (LT4).
    • Increased speed in all body processes is caused by High thyroid hormone present in blood.
    • Reduced thyroid hormone in blood leads to slower body processes.

    Parathyroid Glands

    • The parathyroid gland controls calcium levels in the body.
    • Hyperparathyroidism is high parathyroid hormone, leading to brittle bones (osteoporosis).
    • Hypoparathyroidism is low parathyroid hormone, leading to cardiac arrhythmias, neuromuscular irritability, and tetany.
    • Treatment for hyperparathyroidism is typically surgery. If not a surgical candidate, calcimimetics and bisphosphonates are options.
    • Treatment for hypoparathyroidism involves calcium and 1,25-dihydroxy vitamin D.

    Diseases of the Thyroid

    • Hyperthyroidism ("overactive thyroid gland"): Excess circulating free thyroxine (T4) or free triiodothyronine (T3), or both.
    • Hypothyroidism ("underactive thyroid gland"): Insufficient production of thyroid hormone by the thyroid gland.
    • Major causes of Hyperthyroidism: Graves' disease, Toxic thyroid adenoma, Toxic multinodular goitre.

    Hyperthyroidism - Learning Outcomes

    • LO1: Describe the mechanism of action of drugs used to treat hyperthyroidism or hypothyroidism.
    • LO2: Recall the pharmacokinetics and side effects associated with hyperthyroidism or hypothyroidism treatments.
    • LO3: Describe the mechanism of action of drugs used to treat hyperparathyroidism or hypoparathyroidism.
    • LO4: Recall the pharmacokinetics and side effects associated with hyperparathyroidism or hypoparathyroidism treatments.

    Hyperthyroidism - Signs and Symptoms

    • Signs: Normal/Distorted nail beds angle, clubbed fingers, tremors, diarrhea, menstrual changes (amenorrhea), intolerance to heat, fine/straight hair, bulging eyes, facial flushing, enlarged thyroid, tachycardia, systolic BP increase, weight loss, localized edema.

    Hyperthyroidism - Diagnosis

    • Laboratory: Low serum TSH, High serum T3 and T4, Anti-TSH receptor antibodies.
    • Imaging: Thyroid ultrasound, Radioactive iodine imaging (using Iodine 123) to determine the cause of hyperthyroidism.

    Hyperthyroidism - Imaging

    • Cold Nodule, Grave's Disease, Toxic Multinodular, Hot Nodule, Autonomous Nodule, Thyroiditis
    • Imaging helps identify the cause through visual characteristics of the thyroid gland.

    Synthesis of Thyroid Hormones

    • Iodide trapping (1st step)
    • Oxidation and iodination of tyrosine residues on Tg (2nd step)
    • Coupling of iodotyrosine to form T3 & T4 (3rd step)
    • Proteolysis of Tg, releasing T4, T3, and iodotyrosines (4th step)
    • Deiodination (5th Step)

    Thyroid Treatment Options

    • Thioureylenes (e.g., carbimazole, methimazole, propylthiouracil)
    • Radioactive iodine (131I)
    • Surgery

     Thio(n)amides/Thioureylenes - Clinical Use

    • Reduce the level of thyroid hormone
    • Inhibits the enzyme thyroperoxidase.

     Thio(n)amides/Thioureylenes - Pharmacokinetics

    • Carbimazole is rapidly converted to methimazole.
    • PTU has a half-life of 1 hour, methimazole 4–6 hours.
    • There is a latent period of 2-4 weeks before clinical improvement.
    • PTU is protein-bound, while methimazole is not.

     Thio(n)amides/Thioureylenes - Adverse Effects

    • Major: Agranulocytosis (0.1–0.5% risk), which can occur at any time and dosage, potentially fatal.
    • Stop antithyroid medication and monitor CBC with differential if fever or sore throat.
    • If granulocyte count <500, hospitalize and give broad-spectrum antibiotics.

    Thyroid Drugs - When to Use Carbimazole

    • Use carbimazole in all Graves' disease patients, except during the first trimester of pregnancy, thyroid storm, or adverse reactions.

    Radioactive Iodine - Clinical use

    • Reduce the level of thyroid hormone
    • The isotope used is 131I.
    • Incorporated into thyroglobulin.
    • Emits gamma and beta rays (short-range emission).
    • Exerts cytotoxic action (kills cells).
    • Hypothyroidism often develops after treatment.

    Radioactive Iodine - Pharmacokinetics

    • 131 I oral administration (Single dose).
    • Half-life 8 days, effects diminish to undetectable levels by 60 days.
    • Action may take up to 2 weeks to have an effect.
    • Potential adverse effect is nausea.
    • Special precaution - not for pregnant or breastfeeding women or children.

    Surgery

    • Equally effective as other treatments for Graves' disease.
    • Choice of therapy often involves patient-physician discussion.
    • Reasons for choosing surgery include avoiding radioiodine, avoiding side effects of antithyroid drugs needing rapid reduction of hyperthyroidism and large goiters (obstructing the airway).
    • Total thyroidectomy typically leads to hypothyroidism.

    Adjunctive Therapy

    • Iodine or glucocorticoids, used with antithyroid drugs in severe thyrotoxicosis (e.g., thyroid storm).
    • Beta-adrenoceptor antagonists (e.g., propranolol) can inhibit peripheral conversion of T4 to T3, relieving adrenergic symptoms (tremor, palpitations, heat intolerance, nervousness), and are used while waiting for other drugs to take effect.
    • Contraindications: asthma, heart failure, and vasoconstrictor conditions like Raynaud's syndrome.

    Corticosteroids

    • Can inhibit T4 to T3 conversion.
    • Helpful for relieving thyroiditis inflammation/pain, and thyroid eye disease (Graves' disease).

    NSAIDs

    • Used in subacute thyroiditis

    Hypothyroidism

    • Hypothyroidism slows down bodily functions.
    • Major causes include Hashimoto's thyroiditis (tissue destruction by circulating antibodies and lymphocytes), genetic factors, and iatrogenic causes (e.g., post-thyroidectomy or radiation therapy).

    Hypothyroidism - Signs and Symptoms

    • Symptoms: Hair loss, apathy, lethargy, dry (coarse/scaly) skin, muscle aches/weakness, constipation, intolerance to cold, receding hairline, facial edema, extreme fatigue, thick tongue, slow speech, anorexia, brittle nails/hair, menstrual disturbances, late manifestations (hypothermia, bradycardia, weight gain, LOC, thickened skin), cardiac complications.

    Thyroxine & Liothyronine (LT3)

    • Treatment by administering hormone directly.
    • Synthetic thyroxine derivative (Hormone Replacement Therapy)
    • T4 metabolically converts to T3; LT3 is rarely used except for myxedema coma or with combined T4 treatment.
    • Potential side effect is iatrogenic hyperthyroidism (palpitations, nervousness, headache, difficulty sleeping, insomnia, swelling of legs/ankles, weight loss).

    TSH Monitoring

    • Monitoring frequency: every 6 weeks, until the results are normalized.
    • Target TSH normal range: 0.5–4.5 mIU/L (0.5–2.5 mIU/L, or 1–6 mIU/L in older patients).
    • Cannot rely on TSH results in secondary (pituitary) hypothyroidism.

    Calcium Salts

    • Replaces calcium, improves bone mineralisation, and regulates nervous/muscle tissue.
    • Pharmacokinetics: Oral solution (calcium citrate/carbonate), NOT IM (causes necrosis).
    • Side effects mainly include constipation and potentially chronic kidney disease/kidney stones.

    Vitamin D

    • Vitamin D (Calcifediol/calcitriol) binds to vitamin D-binding protein and goes throughout the body.
    • Promotes calcium absorption.
    • Maintains calcium & phosphate levels, important for bone mineralisation.
    • Potential side effects include allergic skin reactions, calcium buildup in arteries, and cholesterol changes.
    • Monitor serum and urinary Ca2+ levels.

    Hyperparathyroidism

    • Causes of primary hyperparathyroidism include benign growth (adenoma) on one or more glands.
    • Enlargement of two or more glands also common.

    Treatment Options for Hyperparathyroidism

    • Treatment of choice is surgery: removal of one or more glands.
    • Minimally Invasive Radioguided Parathyroidectomy (MIRP) also performed.

    Calcimimetics

    • Mimics calcium circulating in the blood, causing the parathyroid gland to release less parathyroid hormone.

    Bisphosphonates

    • Possible mechanism of action includes inhibiting osteoclast recruitment or inducing osteoclast apoptosis.
    • Used for osteoporosis treatment, increasing bone density up to 10% in three years and decreasing fracture incidence.
    • Systemic bioavailability is about 0.6–0.7% for women and men when under fasting conditions.

    Hypoparathyroidism

    • Caused by inadequate parathyroid hormone resulting in lower than normal calcium in body fluids (i.e., hypocalcemia).

    Hypoparathyroidism - Causes

    • Post-surgical: following total thyroidectomy or radical neck dissection.
    • Infiltrative diseases: Hemochromatosis, Wilson's disease.
    • Hypomagnesemia: Decreased functional activation of adenylate cyclase leads to decreased PTH activity.
    • Congenital defects in DiGeorge syndrome (formation of branchial pouches 3, 4, and 5), Familial syndromes (e.g., autoimmune polyglandular syndrome type 1), and hereditary resistance to parathyroid hormone (pseudohypoparathyroidism).
    • Renal tubule dysfunction where they fail to respond to the presence of parathyroid hormone.

    Questions & Answers (Q&A)

    • Q1: The most serious side effect of carbimazole in a patient with Graves' disease is agranulocytosis.
    • Q2: Carbimazole blocks the synthesis of thyroid hormone.

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    Description

    Test your knowledge on thyroid disorders including hyperthyroidism and hypothyroidism. This quiz covers causes, treatments, laboratory findings, and imaging methods related to thyroid conditions. Challenge yourself to see how well you understand these critical endocrine issues.

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