What might be a common symptom of hyperthyroidism?

Increased heart rate is a common symptom of hyperthyroidism due to the overproduction of thyroid hormones, which significantly ramp up the body's metabolism. This heightened metabolic state causes the heart to work harder and beat faster in order to meet the increased energy demands of the body. As a result, individuals with hyperthyroidism may experience palpitations or a persistent racing heartbeat, which can manifest as increased heart rate.

Understanding the role of thyroid hormones helps clarify this symptom. Thyroid hormones are critical in regulating numerous bodily functions, including heart rate and energy expenditure. When these hormones are overproduced, it disrupts normal physiological balance, leading to symptoms that can be both distressing and problematic.

The other options listed reflect symptoms that are more aligned with conditions opposite to hyperthyroidism, such as hypothyroidism, where individuals might typically experience weight gain, fatigue, and cold intolerance. Therefore, the physiological mechanisms involved in hyperthyroidism directly explain why increased heart rate stands out as a key symptom in this condition.