What is characteristic of hyperthyroidism?

Hyperthyroidism is characterized by the over-production of thyroid hormones, specifically thyroxine (T4) and triiodothyronine (T3). This condition results in an accelerated metabolism in the body, which can lead to symptoms such as weight loss, increased appetite, rapid heartbeat, sweating, anxiety, and nervousness. The excess hormones stimulate many bodily functions, creating a state of heightened physiological activity.

The other options suggest a deficiency or normal production of thyroid hormones, which are conditions associated with hypothyroidism or a euthyroid state, rather than hyperthyroidism. By identifying hyperthyroidism with over-production, one can better understand its effects on metabolism and overall health.