Final answer:
Hyperthyroidism caused by the excessive thyroid hormone thyroxine can result in an increased heart rate and a weakened heart. This condition enhances the metabolic rate and affects the heart's contractility, leading to potential long-term heart complications.
Step-by-step explanation:
The chronic release of excess thyroxine, a condition known as hyperthyroidism, can lead to a sustained increase in heart rate (tachycardia) and can eventually weaken the heart muscle. Thyroxine is a thyroid hormone that, at normal levels, helps regulate the body's metabolism, energy production, and cardiac function. However, when in excess due to an overactive thyroid gland or disorders such as Graves' disease, the balance is disrupted. This hormone directly enters cardiomyocytes and alters activity at the genome level, increasing the metabolic rate, leading to symptoms like weight loss, heat intolerance, and sweating. The physiological effects on the heart include increasing cardiac rate and contractility, which can have detrimental effects if sustained over time. Maintaining hormonal balance is essential to prevent such cardiac issues and overall health complications.