Which hormone is least likely to be released during a marathon?

• A. Adrenaline
• B. Atrial natriuretic peptide (ANP)
• C. Cortisol
• D. Growth hormone

Answer: (B)

Endurance exercise mainly triggers hormones that boost energy availability and cardiovascular support. During a marathon, adrenaline surges to raise heart rate and blood flow to muscles, helping mobilize glucose and fatty acids for quick energy. Cortisol helps maintain blood glucose and supports metabolism during prolonged activity, while growth hormone promotes fat breakdown and helps sustain energy over time.

Atrial natriuretic peptide, on the other hand, is released in response to atrial stretch when there is increased blood volume and pressure, prompting the kidneys to excrete salt and water. In a marathon, substantial sweating reduces plasma volume, which lowers atrial stretch rather than increases it. So ANP release is less likely during the race, making it the least likely hormone to be released in that context.