What is the systemic effect of hyperthyroidism that can explain elevated heart rate and anxiety?

The systemic effect of hyperthyroidism that explains elevated heart rate and anxiety is primarily due to increased metabolism. In hyperthyroidism, there is an overproduction of thyroid hormones, particularly thyroxine (T4) and triiodothyronine (T3), which leads to an overall acceleration of metabolic processes in the body.

This increased metabolic rate results in heightened energy expenditure, which can cause symptoms such as palpitations, anxiety, weight loss, increased body temperature, and increased sweating. The elevated heart rate, or tachycardia, is a direct consequence of increased metabolic activity; the body is essentially in a state of heightened alertness and preparedness, leading to many of the manifestations associated with hyperthyroidism.

Additionally, the overactivity of the thyroid hormones can enhance the responsiveness of the adrenergic system, which further contributes to feelings of anxiety and can elevate heart rate. While fluid retention and an epinephrine surge may be involved in certain scenarios, they do not directly encapsulate the broad systemic changes that occur with hyperthyroidism nor account for the primary symptoms of elevated heart rate and anxiety as effectively as increased metabolism does. Insulin resistance is also not a primary feature of hyperthyroidism and thus does not relate to