Which of the following hormones increase the sensitivity of heart to epinephrine?

 # Which of the following hormones increase the sensitivity of heart to epinephrine?

A. Parathyroid

B. Insulin

C. Thyroid

D. Glucagon

The correct answer is:

C. Thyroid

Explanation:

Thyroid hormones (primarily T3 and T4) increase the sensitivity of the heart to catecholamines, including epinephrine. This effect is due to:

• Increased β-adrenergic receptor density: Thyroid hormones upregulate the expression of β-adrenergic receptors in the heart, enhancing responsiveness to epinephrine and norepinephrine.
• Increased myocardial contractility and heart rate: By amplifying the effects of catecholamines, thyroid hormones contribute to increased cardiac output and sympathetic tone.

Other options:

• A. Parathyroid hormone (PTH): This hormone regulates calcium and phosphate metabolism, with no direct role in cardiac sensitivity to epinephrine.
• B. Insulin: While insulin affects glucose metabolism and has some cardiovascular effects, it does not directly increase heart sensitivity to epinephrine.
• D. Glucagon: Glucagon has some inotropic and chronotropic effects on the heart, but it does not enhance the heart's sensitivity to epinephrine.

Thyroid hormones play a key role in modulating the cardiovascular system, particularly through their interaction with catecholamines.