Clinical Features of Hyperthyroidism
The typical clinical picture of hyperthyroidism includes weight loss (a), tachyarrhythmias (c), and increased tendon reflexes (e), while intolerance to cold and constipation are features of hypothyroidism, not hyperthyroidism.
Correct Features of Hyperthyroidism
Weight Loss
- Weight loss is a cardinal feature of hyperthyroidism, resulting from increased metabolic rate and catabolism despite normal or increased appetite 1, 2, 3
- The American College of Cardiology specifically lists weight loss as a characteristic clinical manifestation of hyperthyroidism 1
- Weight loss occurs in 87.9-93.8% of hyperthyroid patients across age groups 4
Tachyarrhythmias
- Tachycardia and cardiac arrhythmias are prominent cardiovascular manifestations of hyperthyroidism 1, 2, 5
- The American Heart Association emphasizes that hyperthyroidism presents with tachycardia and palpitations as direct effects of excess thyroid hormone on cardiac tissue 2
- Atrial fibrillation is particularly common in elderly hyperthyroid patients 4
- Palpitations occur in 83.3-93.1% of hyperthyroid patients 4
Increased Tendon Reflexes
- Hyperreflexia (increased tendon reflexes) is a characteristic neurological finding in hyperthyroidism, contrasting with the delayed ankle reflexes seen in hypothyroidism 1, 6
- Fine tremor of outstretched hands is another neurological manifestation that accompanies hyperreflexia 1, 2
Incorrect Features (These Indicate Hypothyroidism)
Cold Intolerance (NOT Hyperthyroidism)
- Heat intolerance, not cold intolerance, is the hallmark of hyperthyroidism 1, 2, 3
- The American College of Cardiology explicitly lists "warm, moist skin" and "heat intolerance" as features of hyperthyroidism 1
- Cold intolerance is characteristic of hypothyroidism, where decreased metabolic rate reduces heat production 1, 6
Constipation (NOT Hyperthyroidism)
- Diarrhea, not constipation, occurs in hyperthyroidism due to increased gastrointestinal motility from elevated thyroid hormone 1, 2
- Constipation is a feature of hypothyroidism, where decreased metabolic activity slows bowel transit 1, 6
Additional Classic Features to Recognize
The complete clinical syndrome includes:
- Warm, moist skin with excessive sweating (hyperhidrosis) 1, 2, 6
- Nervousness, tremulousness, anxiety, and insomnia from increased adrenergic tone 1, 2, 5
- Lid lag on physical examination 1, 2
- Proximal muscle weakness despite hyperreflexia 1
- Goiter (palpable thyroid enlargement) in most cases 1, 3
Critical Clinical Pitfall
Do not rely solely on classic hyperadrenergic symptoms in elderly patients, as older adults frequently present with atypical or "apathetic" hyperthyroidism characterized by weakness, anorexia, and atrial fibrillation without the typical features of heat intolerance, tremor, or goiter 4, 7, 8. The American Family Physicians warns that unexplained atrial fibrillation, weakness, and anorexia should prompt thyroid testing even when typical hyperthyroid features are absent 4.