Which endocrine change is listed as a cause of tachycardia?

Which endocrine change is listed as a cause of tachycardia?

• A. Hypothyroidism
• B. Hyperthyroidism
• C. Hyperkalemia
• D. Hypoglycemia

Answer: (B)

Excess thyroid hormone drives faster heart rates. Thyroid hormones increase the sinoatrial node’s automaticity and boost the heart’s responsiveness to sympathetic signals by upregulating beta-adrenergic receptors. In hyperthyroidism, this hormonal excess raises the resting heart rate and often causes persistent tachycardia and palpitations, and can even lead to arrhythmias like atrial fibrillation. The other options don’t typically produce a sustained increase in heart rate: hypothyroidism tends to slow the heart; hyperkalemia disrupts conduction and can slow or irregularize the rhythm; hypoglycemia can trigger a brief adrenergic surge that raises rate, but it’s not the prototypical endocrine cause of tachycardia.

Excess thyroid hormone drives faster heart rates. Thyroid hormones increase the sinoatrial node’s automaticity and boost the heart’s responsiveness to sympathetic signals by upregulating beta-adrenergic receptors. In hyperthyroidism, this hormonal excess raises the resting heart rate and often causes persistent tachycardia and palpitations, and can even lead to arrhythmias like atrial fibrillation. The other options don’t typically produce a sustained increase in heart rate: hypothyroidism tends to slow the heart; hyperkalemia disrupts conduction and can slow or irregularize the rhythm; hypoglycemia can trigger a brief adrenergic surge that raises rate, but it’s not the prototypical endocrine cause of tachycardia.