Hyperthyroidism vs Hypothyroidism
Hyperthyroidism and Hypothyroidism are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.
Hyperthyroidism vs Hypothyroidism at a glance
- Hyperthyroidism: Autoimmune diffuse goiter driven by TSH-receptor stimulating antibodies; most common cause of overt hyperthyroidism.
- Hypothyroidism: Autoimmune chronic lymphocytic thyroiditis; most common cause of hypothyroidism in iodine-replete regions.
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Side-by-side comparison
| Feature | Hyperthyroidism | Hypothyroidism |
|---|---|---|
| At a glance | Autoimmune diffuse goiter driven by TSH-receptor stimulating antibodies; most common cause of overt hyperthyroidism. | Autoimmune chronic lymphocytic thyroiditis; most common cause of hypothyroidism in iodine-replete regions. |
| Classic presentation | Young woman with weight loss, palpitations, anxiety, diffuse goiter with bruit, and proptosis = Graves disease.; Heat intolerance, sweating, palpitations, tremor, anxiety, insomnia; Unintentional weight loss despite increased appetite; Frequent loose stools, oligomenorrhea, proximal muscle weakness; Gritty, bulging eyes; diplopia;… | Middle-aged woman with fatigue, weight gain, cold intolerance, diffuse firm bumpy goiter, and delayed reflex relaxation.; Fatigue, cold intolerance, weight gain, constipation; Dry skin, hair loss (lateral third of eyebrows), brittle nails; Menstrual irregularity (menorrhagia in early disease), infertility; Depression, cognitive slowing,… |
| Workup / key labs | Suppressed TSH + elevated free T4 and/or T3 + positive TRAb, or diffuse uptake on RAIU scan. Orbitopathy or pretibial myxedema with biochemical thyrotoxicosis is sufficient even without antibody confirmation.; TSH (suppressed, <0.01 in overt disease) — most sensitive initial test; Free T4 and total T3 (elevated; T3-predominant toxicosis… | Elevated TSH with low free T4 (overt) or normal free T4 (subclinical), supported by positive anti-TPO antibodies.; TSH — elevated (most sensitive screening test); Free T4 — low in overt disease; normal in subclinical disease; Anti-TPO antibodies — positive in 90-95% of Hashimoto cases (also anti-thyroglobulin in ~60%); Lipid panel… |
| Imaging | Radioactive iodine uptake and scan (RAIU/scan) — diffuse, homogeneous, ELEVATED uptake confirms Graves; differentiates from low-uptake thyroiditis and factitious; Thyroid ultrasound with color Doppler — hypervascular (thyroid inferno) in Graves; useful when RAIU contraindicated (pregnancy, lactation, recent iodine); Orbital CT/MRI… | Ultrasound only if nodule, asymmetry, or compressive symptoms — heterogeneous hypoechoic pattern with pseudonodules typical of Hashimoto; RAIU not routinely indicated |
| First-line treatment | Beta-blocker for adrenergic symptoms — propranolol 20-40 mg q6h (also blocks peripheral T4→T3 conversion at high dose) or atenolol/metoprolol; use cautiously in HF; Thionamide — methimazole 10-40 mg daily (first-line in non-pregnancy; longer half-life; less hepatotoxicity); propylthiouracil (PTU) preferred in 1st trimester pregnancy and… | Levothyroxine (synthetic T4) — start 1.6 mcg/kg/day in healthy young adults; start lower (25-50 mcg) in elderly or known CAD; take on empty stomach 30-60 min before food or 4 h after; separate from calcium, iron, PPIs, fiber, soy; Recheck TSH at 6-8 weeks after initiation or dose change; goal TSH 0.5-2.5 (lower end in pregnancy: 0.1-2.5… |
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