Thyroid Disorders — Comprehensive

Hyper/hypothyroidism, thyroiditis, thyroid storm, thyroid nodule.

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◆Hyperthyroidism causes

•Graves disease: TSI antibodies + diffuse goiter + exophthalmos + pretibial myxedema; high RAIU diffuse
•Toxic multinodular goiter (Plummer): elderly; nodular uptake on scan
•Toxic adenoma: single 'hot' nodule
•Painful subacute (de Quervain) thyroiditis: post-viral; tender goiter; transient hyper → hypo → euthyroid; LOW RAIU (released stored hormone)
•Painless (silent/postpartum) thyroiditis: similar but no pain; postpartum common
•Factitious (exogenous): LOW thyroglobulin (vs all others which are high or normal)

•Methimazole first-line (except first trimester pregnancy — use PTU)
•PTU also used in thyroid storm (blocks T4→T3 conversion)
•Radioactive iodine ablation: definitive; avoid in pregnancy/breastfeeding/severe ophthalmopathy
•Thyroidectomy: large goiter, ophthalmopathy, pregnancy
•β-blocker for symptoms (propranolol)

•Severe hyperthyroidism + fever + tachycardia + agitation/coma + GI symptoms
•Triggers: surgery, infection, iodine load, parturition
•Burch-Wartofsky score for diagnosis
•Treatment ORDER matters:
•1. β-blocker (propranolol) — symptoms
•2. PTU or methimazole — blocks new hormone synthesis
•3. Iodine (Lugol) ≥1 hr AFTER PTU (Wolff-Chaikoff)
•4. Glucocorticoid (hydrocortisone) — blocks T4→T3 conversion + treats possible adrenal insufficiency
•Cooling, IV fluids, treat precipitant

•Hashimoto thyroiditis: most common cause; anti-TPO + anti-thyroglobulin antibodies; ↑ TSH + ↓ free T4; goiter
•Other: post-RAI/surgery, iodine deficiency, lithium, amiodarone, congenital
•Subclinical: ↑TSH + normal T4 — treat if TSH >10, symptomatic, or trying to conceive
•Treatment: levothyroxine; pregnancy increases dose ~30%

•Severe hypothyroidism + AMS + hypothermia + hypoventilation + bradycardia
•IV levothyroxine + IV hydrocortisone (until adrenal insufficiency excluded) + supportive

•Papillary (#1, best prognosis): psammoma bodies + 'Orphan Annie' nuclei; spreads via lymph; thyroidectomy
•Follicular: hematogenous spread (bone, lung)
•Medullary: from parafollicular C cells; ↑calcitonin; MEN 2A/2B
•Anaplastic: elderly; rapidly progressive; poor prognosis

◆PTU = Pregnancy (first trimester) + Thyroid storm (blocks T4→T3); methimazole otherwise
◆Iodine in thyroid storm must come AFTER thionamide to avoid Jod-Basedow + Wolff-Chaikoff
◆Low RAIU + hyperthyroid = thyroiditis, exogenous hormone, iodine load
◆Pregnancy + Graves → PTU (1st trimester) → methimazole (2nd/3rd)
◆Amiodarone = iodine-rich → can cause hyper or hypothyroid; monitor TFTs
◆Hashimoto: 80x risk of thyroid lymphoma

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