Final answer:
A decreased basal metabolic rate is not a symptom of hyperthyroidism; instead, it's a symptom of hypothyroidism. Hyperthyroidism is characterized by an elevated level of thyroid hormone and an increased metabolic rate.
Step-by-step explanation:
The symptoms of Hyperthyroidism include increased heat production, dyspnea (shortness of breath), and increased cardiac output. However, the symptom that does not belong to hyperthyroidism is a decreased basal metabolic rate. Hyperthyroidism is characterized by an elevated level of thyroid hormone in the blood, which leads to an increased metabolic rate, not a decreased one. Symptoms such as weight loss, excessive sweating, diarrhea, muscle weakness, and unusual sensitivity to heat are typically associated with an increased metabolism due to the overactivity of the thyroid gland. In contrast, symptoms like a decreased basal metabolic rate would be associated with hypothyroidism, which is a condition where the thyroid gland is underactive.