During a marathon, which hormone is least likely to be released by the runner?

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

Answer: (B)

During a marathon, the body’s immediate needs are to mobilize energy and maintain blood flow to working muscles, so hormones that support rapid energy availability and sympathetic activation dominate. Adrenaline (epinephrine) is released to increase heart rate, improve blood flow to muscles, and stimulate glucose release. Cortisol rises to sustain glucose production and promote energy availability during prolonged exertion. Growth hormone increases to support long-term energy supply, including fat mobilization. Atrial natriuretic peptide, by contrast, is released mainly in response to atrial stretch from increased blood volume and pressure to promote sodium and water excretion and reduce preload. While exercise does affect blood flow and volume, the primary acute hormonal signals during sustained running are sympathetic and metabolic, making ANP release less typical in this scenario. So ANP is the least likely among these hormones to be released during a marathon.