P.04.02 THYROID AND ANTITHYROID DRUGS
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Questions and Answers

What is the recommended time window for administering levothyroxine in relation to meals?

  • 60 minutes before meals or 4 hours after meals (correct)
  • 30 minutes before meals or 2 hours after meals
  • 45 minutes before meals or 3 hours after meals
  • 90 minutes before meals or 6 hours after meals

    • Why should levothyroxine dosage changes be made slowly?

  • To prevent allergic reactions
  • To reduce the risk of overdose
  • To minimize the risk of drug interactions
  • To avoid transient serum alterations (correct)

    • What is the half-life of levothyroxine?

  • 7 days (correct)
  • 24 hours
  • 48 hours
  • 12 hours

    • Why is liotyronine (T3) not recommended for long-term use?

    <p>It has a shorter half-life and requires multiple daily doses</p> Signup and view all the answers

    What is the clinical indication for levothyroxine administration?

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

    What is the most appropriate initial levothyroxine replacement dose for a young patient with no cardiac disease?

    <p>1.7 mcg/kg/day</p> Signup and view all the answers

    Why should levothyroxine be taken orally on an empty stomach or at bedtime?

    <p>To ensure optimal absorption</p> Signup and view all the answers

    When should thyroid function tests be monitored after starting levothyroxine therapy?

    <p>After 6-8 weeks</p> Signup and view all the answers

    Why might lower thyroxine doses be considered for a patient taking omeprazole?

    <p>Omeprazole interferes with levothyroxine absorption</p> Signup and view all the answers

    When should levothyroxine administration be separated from calcium intake?

    <p>4 hours before calcium intake</p> Signup and view all the answers

    What is the primary reason for the initial methimazole treatment being preferred over propylthiouracil?

    <p>Methimazole has a longer duration of action and can be dosed once daily</p> Signup and view all the answers

    What is the rationale for preferring once daily dosing of methimazole over propylthiouracil?

    <p>Methimazole has a longer half-life</p> Signup and view all the answers

    What is the recommended administration frequency for methimazole?

    <p>Every 6-8 hours</p> Signup and view all the answers

    Why was methimazole preferred over propylthiouracil for initial treatment?

    <p>Methimazole has an improved safety profile</p> Signup and view all the answers

    What is the role of serum FT4 and FT3 concentrations in determining the hormone's biological activity?

    <p>They exist in the free form and determine the hormone's biological activity</p> Signup and view all the answers

    What is the primary mechanism by which T4 is converted to T3?

    <p>Deiodinases in peripheral tissues such as kidneys and liver convert T4 to T3</p> Signup and view all the answers

    What is the preferable practice for patients using levothyroxine to avoid changes in bioavailability?

    <p>Remaining on a consistent levothyroxine preparation between refills</p> Signup and view all the answers

    Which type of thyroxine is the preparation of choice for thyroid replacement and suppression therapy?

    <p>Levothyroxine (T4)</p> Signup and view all the answers

    Which component is responsible for the stability and content uniformity of levothyroxine preparations?

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

    What is the effect of iodide therapy on the size and vascularity of a hyperplastic thyroid gland?

    <p>It decreases the size and vascularity</p> Signup and view all the answers

    When is iodide therapy clinically indicated for thyroid storm?

    <p>As a first-line treatment</p> Signup and view all the answers

    Why should chronic use of iodides in pregnancy be avoided?

    <p>They may cause fetal goiter as they cross the placenta</p> Signup and view all the answers

    What are the disadvantages of iodide therapy?

    <p>All of the above</p> Signup and view all the answers

    What are the toxicities associated with chronic use of iodides?

    <p>Swollen salivary glands and mucous membrane ulcerations</p> Signup and view all the answers

    Which antithyroid medication is preferably given in the 1st trimester of pregnancy due to its strong protein binding and reduced placental crossing?

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

    What is the primary pharmacodynamic action of thioamides like Methimazole and Propylthiouracil?

    <p>Inhibiting the thyroid peroxidase-catalyzed reactions</p> Signup and view all the answers

    Which antithyroid medication inhibits peripheral deiodination of T4 to T3?

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

    What is the most dangerous adverse reaction associated with thioamides like Methimazole and Propylthiouracil?

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

    Why are iodides rarely used as sole therapy for hyperthyroidism today?

    <p>They are ineffective at inhibiting hormone synthesis</p> Signup and view all the answers

    What effect do thioamides have on hormone synthesis?

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

    What distinguishes the onset of thioamides from other antithyroid agents?

    <p>Slow onset requiring 3 - 4 weeks before T4 stores are depleted</p> Signup and view all the answers

    What is the reported incidence of severe hepatitis associated with Propylthiouracil (PTU) use?

    <p>~3%</p> Signup and view all the answers

    Which antithyroid medication is associated with a higher incidence of cholestatic jaundice?

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

    What percentage of patients experience agranulocytosis due to thioamide treatment?

    <p>&lt;0.1%</p> Signup and view all the answers

    Which of the following is a characteristic symptom of hyperthyroidism?

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

    Which antithyroid drug has a half-life of about 1.5 hours?

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

    Which of the following drugs is an active metabolite of Carbimazole?

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

    What is the primary pharmacological action of Propylthiouracil?

    <p>Inhibits peripheral deiodination of T4 to T3</p> Signup and view all the answers

    What is the preferable and effective strategy for definitive treatment of hyperthyroidism before becoming pregnant?

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

    What is the effect of radioactive iodine (RAI) therapy on JP's thyroid function?

    <p>It caused hypothyroidism and required levothyroxine replacement therapy.</p> Signup and view all the answers

    Why did JP receive calcium carbonate three times daily?

    <p>To manage the bone complications associated with her thyroid condition.</p> Signup and view all the answers

    What is the significance of JP's delayed reflexes on physical examination?

    <p>Suggests hypothyroidism and reduced nerve conduction velocity.</p> Signup and view all the answers

    What is the primary reason for JP's weight gain despite experiencing symptoms of hyperthyroidism previously?

    <p>The metabolic changes associated with hypothyroidism caused weight gain.</p> Signup and view all the answers

    Why did JP receive omeprazole?

    <p>To counteract the gastrointestinal side effects of methimazole and propranolol.</p> Signup and view all the answers

    What is the primary cause of primary hypothyroidism?

    <p>Defects in the thyroid gland</p> Signup and view all the answers

    Which medication is part of the treatment protocol for differentiated thyroid cancer to prevent recurrence after total thyroidectomy?

    <p>Radioactive iodine</p> Signup and view all the answers

    What is the primary mechanism of action of anti-thyroid hormones like Methimazole and Carbimazole?

    <p>Inhibiting the conversion of T4 to T3</p> Signup and view all the answers

    What is the primary cause of secondary or central hypothyroidism?

    <p>Defects at the level of the pituitary gland or hypothalamus</p> Signup and view all the answers

    Which type of antithyroid medication reduces thyroid activity and hormone effects by interfering with the production of thyroid hormones?

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

    Which drug is indicated for the preoperative preparation of a hyperplastic thyroid gland to decrease size and vascularity?

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

    What is the primary disadvantage of iodide therapy?

    <p>Increase in intraglandular stores of iodine</p> Signup and view all the answers

    What is a potential adverse reaction associated with chronic use of iodides?

    <p>Bleeding disorders</p> Signup and view all the answers

    In which clinical condition is iodide therapy contraindicated?

    <p>Fetal goiter in pregnancy</p> Signup and view all the answers

    What effect does iodide therapy have on a hyperplastic thyroid gland?

    <p>Reduces size and vascularity</p> Signup and view all the answers

    How is radioactive iodine administered for the treatment of thyrotoxicosis?

    <p>Orally in solution as sodium 131I</p> Signup and view all the answers

    What is the effective half-life of the β rays emitted by radioactive iodine for the treatment of thyrotoxicosis?

    <p>5 days</p> Signup and view all the answers

    What is a significant advantage of radioiodine therapy for hyperthyroidism?

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

    Why should radioactive iodine not be administered to pregnant women or nursing mothers?

    <p>It destroys the fetal thyroid gland and is excreted in breast milk</p> Signup and view all the answers

    What clinical syndrome results from tissues being exposed to high levels of thyroid hormone?

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

    What is the optimal TSH range that should be maintained for patients undergoing levothyroxine therapy?

    <p>0.5–2.5 mIU/L</p> Signup and view all the answers

    What is the suggested time interval for separating levothyroxine administration from calcium intake to ensure optimal absorption?

    <p>4 hours</p> Signup and view all the answers

    What may be a reason for inadequate levothyroxine replacement in a patient with an elevated TSH level?

    <p>Concurrent administration with omeprazole</p> Signup and view all the answers

    What is the suggested approach to optimize levothyroxine absorption in a patient taking omeprazole?

    <p>Stopping omeprazole altogether</p> Signup and view all the answers

    When should thyroid function tests be monitored after starting levothyroxine therapy?

    <p>After 6–8 weeks</p> Signup and view all the answers

    What is the effect of chronic use of iodides in pregnancy?

    <p>Increased risk of hyperthyroidism in the newborn</p> Signup and view all the answers

    For whom may once weekly thyroxine injections be effective?

    <p>Patients who struggle with daily medication adherence</p> Signup and view all the answers

    Which antithyroid medication inhibits peripheral deiodination of T4 to T3?

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

    Why might lower thyroxine doses also be considered for a patient taking omeprazole?

    <p>Omeprazole impairs levothyroxine absorption</p> Signup and view all the answers

    What is the primary role of TSH Releasing Hormone (TRH) in regulating thyroid hormones?

    <p>Signaling the hypothalamus to produce more or less TSH</p> Signup and view all the answers

    What is the physiological consequence of low levels of T3 and T4 in the blood?

    <p>Increased release of TSH by the pituitary gland</p> Signup and view all the answers

    What is the exclusive physiological role of iodine in relation to thyroid hormones?

    <p>Essential for normal synthesis of thyroid hormones</p> Signup and view all the answers

    Which organ plays a critical role in regulating metabolic activities such as body temperature and menstrual cycles?

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

    What is the primary function of THYROXINE (T4) and TRIIODOTHYRONINE (T3) in the body?

    <p>Determinants of brain and somatic development</p> Signup and view all the answers

    What is the recommended time window for administering levothyroxine in relation to meals?

    <p>60 minutes before meals</p> Signup and view all the answers

    Why is liotyronine (T3) not recommended for long-term use?

    <p>It requires multiple daily doses</p> Signup and view all the answers

    What is the optimal TSH range that should be maintained for patients undergoing levothyroxine therapy?

    <p>0.5–2.5 mIU/L</p> Signup and view all the answers

    What is the primary pharmacological action of Propylthiouracil?

    <p>Suppressing thyroid hormone production</p> Signup and view all the answers

    What effect do certain foods and drugs have on the absorption of levothyroxine?

    <p>Impair its absorption</p> Signup and view all the answers

    What is the primary clinical indication for thyroid storm?

    <p>Improvement in thyrotoxic symptoms</p> Signup and view all the answers

    Which of the following is a disadvantage of iodide therapy?

    <p>Delay in the onset of thioamide therapy</p> Signup and view all the answers

    What is the potential toxicity associated with chronic use of iodides in pregnancy?

    <p>Fetal goiter and crossing the placenta</p> Signup and view all the answers

    What is the primary adverse reaction to iodine (IODISM)?

    <p>Drug fever and acneiform rash</p> Signup and view all the answers

    Which clinical condition is iodide therapy contraindicated?

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

    What is the most significant advantage of levothyroxine over liothyronine for thyroid hormone replacement therapy?

    <p>Longer duration of action</p> Signup and view all the answers

    In the context of thyroid hormone replacement therapy, which factor favors the use of liothyronine over levothyroxine?

    <p>Rapid relief of symptoms</p> Signup and view all the answers

    In a patient with hypothyroidism, which symptom is most likely to persist despite adequate levothyroxine replacement?

    <p>Puffy face</p> Signup and view all the answers

    Which characteristic best describes the action of thioamides like carbimazole and methimazole in the treatment of hyperthyroidism?

    <p>Inhibition of thyroid hormone release</p> Signup and view all the answers

    In the treatment of neonatal Grave’s disease, which mechanism supports the use of antithyroid drugs like propylthiouracil and methimazole?

    <p>Inhibition of thyroid hormone synthesis</p> Signup and view all the answers

    What is the primary cause of primary hypothyroidism?

    <p>Defects in the thyroid gland itself</p> Signup and view all the answers

    In the context of thyroid hormone replacement therapy, what is the primary function of Thioamides?

    <p>To reduce thyroid activity by interfering with the production of thyroid hormones</p> Signup and view all the answers

    What is the clinical significance of TSH suppression in the context of differentiated thyroid cancer treatment?

    <p>It prevents recurrence after total thyroidectomy</p> Signup and view all the answers

    What is the primary difference between primary hypothyroidism and secondary (central) hypothyroidism?

    <p>Primary hypothyroidism is due to defects in the thyroid gland itself, while secondary hypothyroidism is due to defects at the level of the pituitary gland or hypothalamus</p> Signup and view all the answers

    What is the primary effect of Iodides in the context of anti-thyroid hormones?

    <p>To increase radioiodine uptake in the thyroid gland</p> Signup and view all the answers

    What is the recommended approach to optimize levothyroxine absorption in a patient taking omeprazole?

    <p>Stop omeprazole administration</p> Signup and view all the answers

    Why might lower thyroxine doses be considered for a patient taking omeprazole?

    <p>Omeprazole interferes with levothyroxine absorption</p> Signup and view all the answers

    What is the primary role of liothyronine in thyroid hormone replacement therapy?

    <p>Rapid correction of hypothyroid symptoms</p> Signup and view all the answers

    When should thyroid function tests be monitored after starting levothyroxine therapy?

    <p>After 6–8 weeks</p> Signup and view all the answers

    Why might once weekly thyroxine injections be effective for some patients?

    <p>In case of nonadherence to daily dosing</p> Signup and view all the answers

    What is the primary advantage of using synthetic levothyroxine for thyroid replacement and suppression therapy?

    <p>It provides stability, content uniformity, and easy laboratory measurement of serum levels</p> Signup and view all the answers

    In the context of thyroid hormone replacement, what differentiates levothyroxine from liothyronine?

    <p>Liothyronine has a shorter half-life than levothyroxine</p> Signup and view all the answers

    What is the key consideration for maintaining patients on a consistent levothyroxine preparation between refills?

    <p>To ensure consistency in bioavailability</p> Signup and view all the answers

    In the context of thyroid function evaluation, which combination of hormone levels indicates hyperthyroidism?

    <p>Increased levels of FT4 and FT3, and decreased level of TSH</p> Signup and view all the answers

    What is the primary role of thyroxine-binding globulin (TBG) in the transport of thyroid hormones?

    <p>To transport T4 and T3 in the bloodstream</p> Signup and view all the answers

    What is the primary role of Thyroid-Stimulating Hormone (TSH) in regulating thyroid hormones?

    <p>Increasing the release of TSH when T3 and T4 levels are low</p> Signup and view all the answers

    What is the exclusive physiological role of iodine in relation to thyroid hormones?

    <p>Aiding in the synthesis of thyroid hormones</p> Signup and view all the answers

    What is the primary pharmacodynamic action of thioamides like Methimazole and Propylthiouracil?

    <p>Inhibiting peripheral deiodination of T4 to T3</p> Signup and view all the answers

    What is the suggested approach to optimize levothyroxine absorption in a patient taking omeprazole?

    <p>Administering levothyroxine at least 4 hours apart from omeprazole</p> Signup and view all the answers

    What is the role of serum FT4 and FT3 concentrations in determining the hormone's biological activity?

    <p>Evaluating the biological activity of thyroid hormones</p> Signup and view all the answers

    Why is liotyronine (T3) not recommended for long-term use?

    <p>It has a short half-life and may cause fluctuations in hormone levels</p> Signup and view all the answers

    How does iodide therapy affect the size and vascularity of a hyperplastic thyroid gland?

    <p>It increases the size and vascularity</p> Signup and view all the answers

    Which adverse reaction is more commonly associated with methimazole compared to Propylthiouracil?

    <p>Cholestatic jaundice</p> Signup and view all the answers

    What is the primary mechanism of action of Propylthiouracil in inhibiting hormone synthesis?

    <p>Inhibiting peripheral deiodination of T4 to T3</p> Signup and view all the answers

    What was the major antithyroid agent prior to the introduction of thioamides in the 1940s?

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

    What is the most dangerous complication associated with thioamides like Propylthiouracil and Methimazole?

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

    What is the role of iodides in the context of anti-thyroid hormones?

    <p>Blocking organification of iodine</p> Signup and view all the answers

    What is the primary pharmacological action of Propylthiouracil and Methimazole?

    <p>Inhibition of thyroglobulin proteolysis</p> Signup and view all the answers

    What is the potential toxicity associated with chronic use of iodides in pregnancy?

    <p>Bleeding disorders</p> Signup and view all the answers

    Why are iodides rarely used as sole therapy for hyperthyroidism today?

    <p>They cause an increase in intraglandular stores of iodine</p> Signup and view all the answers

    How does radioactive iodine (RAI) therapy affect thyroid function?

    <p>It reduces the size of hyperplastic thyroid glands</p> Signup and view all the answers

    What is the effect of iodide therapy on a hyperplastic thyroid gland?

    <p>Decreases the size and vascularity</p> Signup and view all the answers

    Which of the following antithyroid medications has a longer duration of action allowing once daily dosing and an improved safety profile?

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

    What is the primary cause of secondary or central hypothyroidism?

    <p>Deficiency in TSH or TRH production by the pituitary or hypothalamus</p> Signup and view all the answers

    What is the potential toxicity associated with chronic use of iodides in pregnancy?

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

    In the context of thyroid function, what effect does iodide therapy have on the size and vascularity of a hyperplastic thyroid gland?

    <p>Increases size and vascularity</p> Signup and view all the answers

    What distinguishes the onset of thioamides like Methimazole from other antithyroid agents?

    <p>Delayed onset of action</p> Signup and view all the answers

    Which medication has the primary pharmacodynamic action of inhibiting thyroid hormone synthesis by interfering with iodine oxidation and organification?

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

    In the context of toxicity, which medication is associated with a rare but serious adverse effect known as agranulocytosis, a significant reduction in white blood cells?

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

    What is the primary reason why radioactive iodine should not be administered to pregnant women or nursing mothers?

    <p>It crosses the placenta to destroy the fetal thyroid gland</p> Signup and view all the answers

    In the context of hyperthyroidism, which medication is contraindicated due to its potential to worsen the condition by causing temporary hypothyroidism followed by a surge in thyroid hormone production?

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

    Which medication is primarily used for the acute management of severe hyperthyroidism such as thyroid storm, due to its additional effect of inhibiting the peripheral conversion of T4 to T3?

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

    What is the primary mechanism of action of Thioamides like Methimazole and Carbimazole?

    <p>Inhibition of thyroid hormone production by interfering with the activity of the enzyme thyroperoxidase</p> Signup and view all the answers

    What is the most significant adverse effect associated with the chronic use of Iodides for hyperthyroidism?

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

    What is the primary pharmacodynamic action of Propylthiouracil (PTU)?

    <p>Inhibition of peripheral deiodination of T4 to T3 in the liver</p> Signup and view all the answers

    What is the effect of radioactive iodine (RAI) therapy on a hyperplastic thyroid gland?

    <p>Decreases its size and vascularity</p> Signup and view all the answers

    In the context of iodide therapy, what is the most common toxicity associated with chronic use?

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

    What is the primary advantage of methimazole over propylthiouracil in the treatment of hyperthyroidism?

    <p>Methimazole has a stronger inhibitory effect on T4 to T3 conversion than propylthiouracil</p> Signup and view all the answers

    In the context of iodide therapy for hyperthyroidism, what is the most significant disadvantage of using iodides?

    <p>Iodides can worsen the vascularity of a hyperplastic thyroid gland</p> Signup and view all the answers

    Why is iodide therapy contraindicated in patients with multinodular goiter?

    <p>Iodides can worsen the vascularity of a hyperplastic thyroid gland</p> Signup and view all the answers

    What is the primary pharmacological action of radioactive iodine in the treatment of hyperthyroidism?

    <p>Selective destruction of thyroid tissue</p> Signup and view all the answers

    Why is methimazole preferred over propylthiouracil for initial treatment in pregnant patients with hyperthyroidism?

    <p>Methimazole has a lower risk of crossing the placenta than propylthiouracil</p> Signup and view all the answers

    What is the primary pharmacological action of Propylthiouracil?

    <p>Inhibits the synthesis of thyroid hormones</p> Signup and view all the answers

    What is the potential toxicity associated with chronic use of iodides in pregnancy?

    <p>Fetal goiter</p> Signup and view all the answers

    What is the primary cause of primary hypothyroidism?

    <p>Inflammatory destruction of the thyroid gland</p> Signup and view all the answers

    What is the primary effect of Iodides in the context of anti-thyroid hormones?

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

    When is iodide therapy clinically indicated for thyroid storm?

    <p>In severe cases of thyrotoxicosis with organ dysfunction</p> Signup and view all the answers

    What is the reported incidence of severe hepatitis associated with Propylthiouracil (PTU) use?

    <p>1 in 1,000,000</p> Signup and view all the answers

    What is the potential adverse reaction associated with chronic use of iodides?

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

    What is the primary role of Thyroid-Stimulating Hormone (TSH) in regulating thyroid hormones?

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

    What is the exclusive physiological role of iodine in relation to thyroid hormones?

    <p>Is essential for hormone synthesis</p> Signup and view all the answers

    What is the primary difference between primary hypothyroidism and secondary (central) hypothyroidism?

    <p>Primary - Increased TSH; Secondary - Decreased TSH</p> Signup and view all the answers

    Study Notes

    Levothyroxine Administration and Monitoring

    • Levothyroxine should be administered on an empty stomach or at bedtime to enhance absorption.
    • Dosage changes for levothyroxine should be made slowly to prevent adverse effects and allow the body to adjust.
    • The half-life of levothyroxine is approximately 7 days, allowing for once-daily dosing.
    • Initial levothyroxine replacement dose recommended for young patients without cardiac disease is typically 1.6 to 1.8 mcg/kg/day.
    • Thyroid function tests should be monitored 6-8 weeks after starting levothyroxine therapy.

    Clinical Indications and Specifics

    • Clinical indication for levothyroxine administration includes hypothyroidism and post-thyroidectomy for cancer.
    • Liothyronine (T3) is not recommended for long-term use due to its shorter half-life and potential fluctuation in hormone levels.
    • Levothyroxine absorption may be affected by calcium intake; separation from calcium supplements is advised.

    Antithyroid Medications

    • Methimazole is preferred over propylthiouracil (PTU) for initial treatment due to its once-daily dosing and lower incidence of adverse effects.
    • Methimazole is associated with fewer side effects and ease of administration compared to PTU.
    • Propylthiouracil inhibits peripheral deiodination of T4 to T3 and is recommended for use in the first trimester of pregnancy due to low placental transfer.
    • Both thioamides, Methimazole and PTU, act by reducing hormone synthesis in the thyroid gland.

    Iodide Therapy

    • Iodide therapy is indicated for reducing size and vascularity of a hyperplastic thyroid gland, especially in preparation for surgery or thyroid storm.
    • Chronic use of iodides during pregnancy should be avoided due to potential fetal toxicity.
    • Iodides are contraindicated in hyperthyroid patients presenting with iodine-induced effects.

    Adverse Reactions and Toxicities

    • Severe hepatitis is a reported adverse reaction associated with PTU use.
    • Agranulocytosis occurs in about 0.5%-1% of patients treated with thioamides.
    • Iodides may cause adverse reactions such as iodism, characterized by symptoms like metallic taste and skin reactions.
    • Chronic iodide therapy may lead to toxicity-related effects and is thus used cautiously.

    Radioactive Iodine Treatment

    • Radioactive iodine therapy is an effective treatment for hyperthyroidism and is contraindicated in pregnant or nursing women due to risks to the fetus or infant.
    • Radioactive iodine is administered orally and is efficient for selective destruction of hyperactive thyroid tissue.

    Thyroid Function and Metabolic Regulation

    • Primary hypothyroidism typically results from autoimmune conditions like Hashimoto's thyroiditis.
    • TSH Releasing Hormone (TRH) stimulates the secretion of TSH, regulating thyroid hormones.
    • The primary function of T4 and T3 is to regulate metabolic processes, including energy expenditure, body temperature, and growth.

    Patient Management Considerations

    • Careful monitoring of thyroxine levels is required, especially in patients on medications like omeprazole that may affect absorption.
    • Once weekly thyroxine injections may be effective for some patients to maintain stable hormone levels, particularly in those with adherence issues.
    • Optimal TSH range for patients on levothyroxine therapy should be between 0.5 and 2.5 mIU/L.

    Key Symptoms and Clinical Indicators

    • Symptoms of hyperthyroidism can include weight loss, heat intolerance, and tachycardia.
    • Inadequate levothyroxine replacement might be observed with elevated TSH levels in patients undergoing treatment.

    Summary of Comparative Efficacy

    • Levothyroxine is preferred for long-term thyroid hormone replacement due to its stable pharmacokinetics and lower risk of fluctuating hormone levels compared to liothyronine.

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