Final answer:
Hyperthyroidism is characterized by symptoms including weight loss, increased appetite, profuse sweating, and an increased heart rate, differentiating it from hypothyroidism, which has opposing signs.
Step-by-step explanation:
The distinguishing manifestation of hyperthyroidism is an elevated level of thyroid hormone in the blood, which leads to an increased metabolic rate. This can result in a combination of symptoms, including weight loss despite increased appetite, profuse sweating, and an increased heart rate. Other symptoms may include heat intolerance, muscle weakness, and difficulty sleeping. These are in direct contrast to hypothyroidism, which typically involves weight gain, cold sensitivity, and a decreased heart rate.