Several hormones contribute to increasing heart rate. The primary hormones responsible are catecholamines, specifically epinephrine (adrenaline) and norepinephrine (noradrenaline).
How Catecholamines Increase Heart Rate
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Mechanism: These hormones, released by the sympathetic nervous system, act on the heart to accelerate its rhythm. As detailed in the Mayo Clinic article on stress, adrenaline increases heart rate and blood pressure. The Yale Medicine article emphasizes noradrenaline's role in increasing heart rate and blood pressure during stress ("fight-or-flight"). The UC Davis Health resource on heart rate further explains the sympathetic nervous system's release of catecholamines to accelerate the heart.
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Example: During a stressful situation, the body releases adrenaline and noradrenaline, leading to a rapid increase in heart rate, preparing the body for action.
Other Hormones Affecting Heart Rate
While catecholamines are the primary drivers, other hormones also influence heart rate:
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Thyroid hormones: As noted in the Harvard Health article and StatPearls resources on thyroid hormones, these hormones influence the force and speed of the heartbeat. They have a permissive effect on the actions of catecholamines, influencing their overall impact on the heart.
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Cortisol: The "stress hormone," cortisol, as described by the Mayo Clinic and StatPearls, increases heart rate and respiratory rate.
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Other Hormones: A PubMed article lists additional hormones that can increase heart rate when present in excess, including endothelins, glucocorticosteroids, leptin, and PTHrP.
Hormonal Fluctuations and Heart Rate
- Menstrual Cycle: Heart rate can fluctuate throughout the menstrual cycle, often increasing slightly during ovulation and the luteal phase, as highlighted by the Cleveland Clinic article on women and heart rate.
- Pregnancy: Studies, like the one referenced from NCBI, show that pregnancy independently influences heart rate, even when accounting for thyroid hormone levels.
Therefore, while adrenaline and noradrenaline are the most prominent hormones increasing heart rate, other hormones contribute and influence the overall effect.
