12. Thyroid and antithyroid drugs. Hypothalamic and pituitary hormones Flashcards

Question

Desmopressin

Answer 1

Selective V2 agonist - Synthetic analogue of ADH (peptide) - Prolonged half-life and duration of action compared to endogenous ADH - IV, intranasal, oral, subcutaneous - Central diabetic insipidus - Hemophilia A – factor VIII deficiency - Von-Willebrand disease ``` Side effects: GI disturbances, headache, hyponatremia, allergic reaction ```

Answer 2

V1, V2 antagonist - IV - SIADH - Offset fluid retention (hyponatremia or heart failure) Side effects: infusion site reaction, osmotic demyelination syndrome due to rapid Na+ correction

Answer 3

Levothyroxine (T4) Synthetic thyroid hormones, used in the management of hypothyroidism. - Activation of nuclear receptors results in gene expression, RNA formation, protein synthesis and subsequent physiological response - Oral, IV - Converted to T3 in target cells, liver, kidneys - Maximum effect is seen after 6-8 weeks of therapy - Hypothyroidism Side effects: symptoms of thyroid excess

Answer 4

- Oral, IV - 10X more potent than T4 - Hypothyroidism; used in case of deiodinase enzyme deficiency (T4 cannot be converted to T3) Side effects: symptoms of thyroid excess

Answer 5

- Essential mineral nutrient, intake with diet - Daily requirement 150 μg - Iodine salt preparation (KI) for replacement therapy - Oral - Dietary iodine deficiency (endemic goiter) - Thyrotoxicosis crisis (high dose suppresses the gland) Side effects: cutaneous and mucus membrane irritation, allergic reaction, hypo-/hyper- thyroiditis

Answer 6

Antithyroid drugs Used in the management of thyroid gland hyperactivity. Thioamides - Inhibit thyroid peroxidase activity - Inhibit peripheral conversion of T4 to T3 (deiodinase enzymes) - Oral - Duration of action 6-8 h' - Requires 3-4 weeks for onset of activity (delayed action since the release of preformed thyroid hormones is not affected) - Hyperthyroidism - Used during pregnancy and lactation ``` Side effects: skin rash, nausea, vasculitis, agranulocytosis, liver dysfunction, hypothyroidism, drug-induced lupus ```

Answer 7

Antithyroid drugs Used in the management of thyroid gland hyperactivity. Thioamides - Inhibit thyroid peroxidase activity - Inhibit peripheral conversion of T4 to T3 (deiodinase enzymes) - Oral - Duration of action 24 h' - Requires 3-4 weeks for onset of activity (delayed action since the release of preformed thyroid hormones is not affected) - No effect on deiodinase enzyme - Hyperthyroidism - Preferred generally (administered once daily) ``` Side effects: skin rash, nausea, vasculitis, agranulocytosis, liver dysfunction, hypothyroidism, drug-induced lupus, teratogenic ('aplasia cutis') ```

Answer 8

- Inhibit tyrosine iodination - Inhibit thyroid hormone release - Reduce the size and vascularity of hyperplastic thyroid gland Lugol's solution (iodine + potassium iodide) Potassium iodide (saturated solution) - Oral - Onset of action within 2-7 days - Effect may be transient (the gland may "escape" the iodide blockage after several weeks of treatment) - Thyroid storm - Preparation for surgical thyroidectomy - Toxicity is generally rare

Answer 9

- Radiation-induced destruction of thyroid parenchyma I131 - Oral - Not to be used during pregnancy and lactation - Hyperthyroidism Side effects: pharyngitis, hypothyroidism

Answer 10

- Competitive inhibitors of iodide transporter – reduce the uptake of iodide by the thyroid gland Thiocyanate (SCN-) Perchlorate (ClO4-) - Unpredictable effect - Rarely used clinically - Iodide-induced hyperthyroidism Side effects: aplastic anemia

Answer 11

- Inhibit peripheral conversion of T4 to T3 (deiodinase enzymes) - Control the tachycardia and other cardiac abnormalities of severe thyrotoxicosis Propranolol - Oral - Rapid onset of activity - Thyroid storm ``` Side effects: bronchospasm, AV block, hypotension, bradycardia ```

Answer 12

- Inhibit peripheral conversion of T4 to T3 (deiodinase enzymes) - Control thyroid ophthalmopathy (seen with Graves' disease) Hydrocortisone Methylprednisolone - Oral or parenteral - Moderate to severe thyroid ophthalmopathy - Thyroid storm

Answer 13

``` Rare condition, presents as a life-threatening exacerbation of hyperthyroidism, accompanied by: 1. fever, 2. delirium, 3. seizures, 4. coma, 5. vomiting, 6. diarrhea, and 7. jaundice. ``` Mortality rate due to cardiac failure, arrhythmia, or hyperthermia is as high as 30%, even with treatment. Thyrotoxic crisis is usually precipitated by acute illness (stroke, infection, trauma, diabetic ketoacidosis), surgery (especially on the thyroid), or radioiodine treatment of a patient with partially treated or untreated hyperthyroidism. Management: - PTU or methimazole (IV bolus, high dose) - Potassium-iodide solution (IV) - β-blockers to control tachycardia and adrenergic symptoms (IV) - Glucocorticoids to control ophthalmopathy (IV) 1st line: Propanolol Propylthiouracil or methimazole hydrocortisone 2nd line Potassium-iodide solution (IV), Lugol solution or sodium iodide Lithium carbonate L-Carnitine support therapy: - depolarising electrolyte solution - Paracetamol - Phenobarbital - Furosemide and ACE-inhibitors in case of cardiac failure selected cases: - assisted mechanical ventilation case of hypoxemia - cooled mattresses and cold blankets in case of hyperthermia (if body temperature > 40°C)

Answer 14

Rare condition, life-threatening exacerbation of hypothyroidism. Presentation: - Hypothermia - Hypoglycemia - Hypotension - Altered mental status Management: - Thyroid hormones (IV) - Glucocorticoids (pituitary-adrenal axis is impaired in severe hypothyroidism) - Supportive management - Elimination of triggering event (if possible)

12. Thyroid and antithyroid drugs. Hypothalamic and pituitary hormones Flashcards

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