Thy Flashcards
(28 cards)
What is the mechanism of action of Lugol’s Iodine?
Produces a rapid ‘thyroid‑constipation’ by blocking multiple steps – inhibits Na⁺/I⁻ symporter expression, interferes with oxidation/iodination, arrests endocytosis of thyroglobulin and proteolysis → immediate fall in T₃/T₄ release.
What are the beneficial effects of Lugol’s Iodine?
Fastest inhibitor with clinical response within 24 h; shrinks, firms and devascularises gland; falls peripheral T₄→T₃ conversion.
What are the indications for using Lugol’s Iodine?
- Pre‑operative preparation in Graves’ disease 2. Thyroid storm 3. Prophylaxis of endemic goitre 4. Topical antiseptic forms.
What are the limitations and adverse effects of Lugol’s Iodine?
‘Thyroid‑escape’ after 14 d → rebound thyrotoxicosis; acute allergy or chronic ‘iodism’; long‑term use → hypothyroidism/goitre.
What precautions should be taken when using Lugol’s Iodine?
Avoid >14 d continuous therapy; do not use in pregnancy/lactation; screen for iodine sensitivity.
What is the mechanism of action of Carbimazole?
Converted to methimazole; binds thyroid peroxidase → blocks iodination & coupling of MIT/DIT.
What are the therapeutic advantages of Carbimazole?
First‑line for Graves’, high potency, reversible hypothyroidism, non‑invasive alternative to surgery.
What are the indications for Carbimazole?
- Definitive therapy in Graves’ disease 2. Pre‑operative euthyroid preparation 3. Short‑term control before/after ¹³¹I.
What are the limitations and adverse effects of Carbimazole?
Latent onset; common GI upset, pruritic rash; serious agranulocytosis.
What precautions should be taken when using Carbimazole?
Avoid high dose in late pregnancy; monitor CBC & LFTs.
What is the mechanism of action of Propylthiouracil (PTU)?
Blocks peripheral 5’-deiodinase (T₄→T₃) conversion.
What are the therapeutic advantages of PTU?
Preferred in 1st‑trimester pregnancy & thyroid storm; safe in children.
What are the indications for PTU?
- Acute thyroid storm 2. Early pregnancy hyperthyroidism 3. Intolerance to carbimazole.
What are the limitations and adverse effects of PTU?
Hepatotoxicity, agranulocytosis, multiple daily dosing affects compliance.
What precautions should be taken when using PTU?
Baseline & periodic liver functions, CBC; instruct patients to report sore throat/jaundice.
What is the mechanism of action of Radioactive Iodine (¹³¹I)?
¹³¹I⁻ concentrates in follicle; β‑particles induce selective necrosis & fibrosis.
What are the advantages of Radioactive Iodine?
Simple outpatient procedure, inexpensive, permanent cure for Graves’ / toxic nodular goitre.
What are the limitations and adverse effects of Radioactive Iodine?
Progressive hypothyroidism; contraindicated in pregnancy & children; neck soreness.
What are the indications for Radioactive Iodine?
- Hyperthyroidism due to Graves’ or toxic multinodular goitre 2. Relapse after surgery or drug therapy.
What precautions should be taken when using Radioactive Iodine?
Stop antithyroid drugs 5–7 d pre‑dose, avoid pregnancy conception for ≥6 mo.
What are the uses of thyroid hormones (levothyroxine/liothyronine)?
- Replacement therapy 2. Myxoedema coma 3. Non‑toxic goitre with iodine deficiency 4. Post‑thyroidectomy for differentiated carcinoma.
Why is Lugol’s iodine given ~10 days before thyroid surgery?
It rapidly blocks hormone release and shrinks, firms and devascularises the gland, making surgery easier.
Why is Propylthiouracil preferred in hyperthyroid pregnancy / thyroid storm?
It blocks peripheral T₄→T₃ conversion, reducing foetal hypothyroid risk.
Why is Carbimazole the drug of choice in Graves’ disease?
High potency with once‑daily dosing, good long‑term remission rates, well tolerated.
