Which of the following is NOT a symptom of hyperthyroidism?

Fatigue is not typically associated with hyperthyroidism, which is characterized by an overactive thyroid gland leading to an excess of thyroid hormones in the body. Instead, the most common symptoms of hyperthyroidism include increased energy levels, weight loss, rapid heart rate (tachycardia), tremors, and in some cases, exophthalmos or bulging eyes. These symptoms arise from the body's heightened metabolic state due to increased thyroid hormone levels.

The presence of exophthalmos, tachycardia, and tremors are directly linked to the physiological effects of thyroid hormone excess, where exophthalmos occurs due to the swelling of tissues behind the eyes, tachycardia is a response to elevated metabolic activity, and tremors can result from increased adrenergic activity. In contrast, fatigue is more commonly a symptom of hypothyroidism, where the underactive thyroid results in reduced metabolic activity and energy levels. Thus, fatigue does not fit into the profile of symptoms one would expect to see in a patient with hyperthyroidism.