Thyroid Disorders: Hyperthyroidism vs Hypothyroidism With Lab Patterns & Management

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Below is your **complete, concise-but-exhaustive NEET PG–style reference** for **Thyroid Disorders: Hyperthyroidism vs Hypothyroidism — Definitions, Pathophysiology, Causes, Clinical Features, Lab Patterns, Diagnosis & Full Management**. --- # **THYROID DISORDERS: HYPERTHYROIDISM vs HYPOTHYROIDISM** **With Lab Patterns, Pathophysiology & Management** --- # **1. DEFINITIONS** ### **Hyperthyroidism** Excess production of thyroid hormones (**↑T3, ↑T4**) causing **increased metabolic rate** and **sympathoadrenal activation**. ### **Hypothyroidism** Deficient production of thyroid hormones (**↓T3, ↓T4**) causing **slowed metabolic processes** and **accumulation of glycosaminoglycans**. --- # **2. PATHOPHYSIOLOGY** ### **Hyperthyroidism** * Excess T3/T4 → ↑β-adrenergic receptor sensitivity → tachycardia, tremors. * Increased mitochondrial oxidative processes → heat intolerance, weight loss. * Autoimmune stimulation (Graves): **TSI (thyroid-stimulating immunoglobulin)** activates TSH receptor → diffuse goitre & ophthalmopathy. ### **Hypothyroidism** * ↓T3/T4 → ↓basal metabolic rate → cold intolerance, fatigue, weight gain. * Accumulation of mucopolysaccharides → **myxedema**, puffy face. * Autoimmune destruction (Hashimoto): **anti-TPO & anti-TG antibodies** attack gland → gradual failure. --- # **3. CAUSES** ### **Hyperthyroidism** **Primary causes (↓TSH):** * **Graves disease (most common)** * Toxic multinodular goitre * Toxic adenoma * Thyroiditis (subacute, silent, postpartum) * Excess iodine (Jod-Basedow) * Amiodarone-induced (type 1 & type 2) * Excess exogenous thyroid hormone **Secondary causes (↑TSH):** * TSH-secreting pituitary adenoma --- ### **Hypothyroidism** **Primary (↑TSH):** * **Hashimoto thyroiditis (most common worldwide)** * Iatrogenic (thyroidectomy, radioactive iodine) * Iodine deficiency (globally common) * Drugs: amiodarone, lithium, anti-thyroid drugs * Congenital hypothyroidism (cretinism) **Secondary (↓TSH & ↓T4):** * Pituitary failure (Sheehan, tumor) --- # **4. CLINICAL FEATURES** ### **Hyperthyroidism – Symptoms** * Weight loss despite increased appetite * Heat intolerance, sweating * Palpitations, tachycardia, AF * Tremors, anxiety, hyperreflexia * Diarrhea * Menstrual irregularities * Fine hair, warm moist skin **Graves-specific:** * Ophthalmopathy (exophthalmos) * Pretibial myxedema * Diffuse goitre with bruit --- ### **Hypothyroidism – Symptoms** * Fatigue, lethargy * Weight gain * Cold intolerance * Bradycardia * Constipation * Dry skin, hair loss * Hoarse voice * Depression * Carpal tunnel syndrome * Hypercholesterolemia (↑LDL) * Heavy menstrual bleeding **Severe:** * **Myxedema coma** → hypothermia, bradycardia, hypoventilation. --- # **5. LAB PATTERNS (MOST IMPORTANT HIGH-YIELD)** | Disorder | TSH | T3/T4 | Additional Clues | | ------------------------------- | ---- | ------------ | ------------------- | | **Primary Hyperthyroidism** | ↓TSH | ↑T3/T4 | Graves: ↑TSI, ↑RAIU | | **Secondary Hyperthyroidism** | ↑TSH | ↑T3/T4 | Pituitary adenoma | | **Thyroiditis (hyper phase)** | ↓TSH | ↑T3/T4 | **Low RAIU** | | **Factitious thyrotoxicosis** | ↓TSH | ↑T3/T4 | **Low Tg level** | | **Primary Hypothyroidism** | ↑TSH | ↓T3/T4 | ↑Anti-TPO | | **Secondary Hypothyroidism** | ↓TSH | ↓T3/T4 | Pituitary disease | | **Subclinical Hyperthyroidism** | ↓TSH | Normal T4/T3 | Risk AF | | **Subclinical Hypothyroidism** | ↑TSH | Normal T4/T3 | Treat if TSH >10 | ### **Radioactive Iodine Uptake (RAIU)** | Condition | RAIU | | -------------------------------- | --------------------- | | Graves | **High diffuse** | | Toxic multinodular goitre | **Patchy high** | | Toxic adenoma | **Single hot nodule** | | Thyroiditis | **Low uptake** | | Excess exogenous thyroid hormone | **Low** | --- # **6. INVESTIGATIONS** * TSH (best screening test) * Free T4, Total/Free T3 * Anti-TPO, Anti-TG antibodies * TSI (for Graves) * RAIU scan * Thyroid ultrasound (nodules) * Lipid profile (hypothyroidism) * ECG (tachycardia, AF) --- # **7. MANAGEMENT** --- ## **A. Hyperthyroidism** ### **1. Symptomatic Control** **β-blocker: Propranolol** * **Dose:** 20–40 mg PO TID * ↓tremor, ↓HR, ↓T4 → T3 conversion --- ### **2. Antithyroid Drugs** | Drug | Mechanism | Dose | Notes | | ---------------------------- | ------------------------------------------ | ------------ | ------------------------------------------- | | **Methimazole (first-line)** | Inhibits TPO → ↓T3/T4 synthesis | 10–30 mg/day | Avoid in 1st trimester | | **Propylthiouracil (PTU)** | Inhibits TPO + peripheral T4→T3 conversion | 100 mg TID | Preferred: **1st trimester, thyroid storm** | **Adverse effects:** Agranulocytosis, rash, hepatotoxicity **Counselling:** Report sore throat/fever immediately (check CBC). --- ### **3. Radioactive Iodine (RAI)** * Definitive therapy for Graves, toxic adenoma * Contraindicated in pregnancy/lactation * May cause later hypothyroidism --- ### **4. Surgery – Thyroidectomy** Indications: * Large goitre * Obstructive symptoms * Suspicious nodules * Pregnancy (2nd trimester if required) --- ### **5. Thyroid Storm (Emergency)** * **PTU 500–1000 mg loading → 250 mg q4h** * **Propranolol** * **IV Hydrocortisone** * **Iodine (Lugol’s) AFTER PTU** * Cooling, fluids, treat trigger --- --- ## **B. Hypothyroidism** ### **1. Levothyroxine Replacement** **Drug of choice**. * **Initial dose:** 1.6 mcg/kg/day (adult) * Elderly or cardiac pts: start 25–50 mcg/day * Take on **empty stomach** 30 min before breakfast. **Monitoring:** * Repeat TSH every 6–8 weeks * Target: normal TSH ### **Drug Interactions (reduce absorption):** * Iron, calcium, PPIs, sucralfate, soy --- ### **2. Myxedema Coma (Emergency)** * **IV Levothyroxine 200–400 mcg bolus** * **IV Hydrocortisone 100 mg q8h** * Warm slowly * Mechanical ventilation if needed * Correct hyponatremia, hypoglycemia --- # **8. DIFFERENTIAL DIAGNOSIS** ### **Hyperthyroidism DDx** * Anxiety disorder * Pheochromocytoma * AF with rapid ventricular response * Drug-induced (amiodarone) ### **Hypothyroidism DDx** * Depression * Anemia * Chronic fatigue syndrome * PCOS (in women) --- # **9. QUICK COMPARISON TABLE** | Feature | Hyper | Hypo | | ----------- | --------------- | --------------- | | Weight | ↓ | ↑ | | HR | Tachycardia | Bradycardia | | Skin | Warm, moist | Dry, coarse | | Bowel | Diarrhea | Constipation | | Cholesterol | ↓ | ↑↑ | | Reflexes | Fast relaxation | Slow relaxation | | TSH | ↓ | ↑ | | T4 | ↑ | ↓ | --- If you want, I can also generate: ✅ **20–40 NEET PG level case-based MCQs on this topic** ✅ **HTML-CSS-JS quiz file** ✅ **SEO-friendly tags + titles for your website** Just tell me **“give MCQs”** or **“give HTML file”**.