2. Sudden weight loss
Many people with overactive thyroid often complain of weight loss and lethargy even when their appetite and the type and amount of food they eat remain the same or even increase in quantity. This is mainly due to an increase in the metabolic rate and BMR in patients with hyperthyroid.
The chances of weight loss is directly related to the severity of the overactive thyroid. As hyperthyroidism also increases the appetite of patients, some patients may not experience weight loss, and some may actually gain weight, depending on their caloric intake and severity of disease.