In most cases, excess thyroid hormone is associated with a high basal metabolic weight. This means that your body burns more energy while it's at rest, so weight loss is a common symptom of hyperthyroidism. This also means that not producing enough thyroid hormone is usually associated with a low basal metabolic rate.

How much weight can you lose with hyperthyroidism?

Even though you may eat constantly, you could lose weight, usually between 5 and 10 pounds—even more in extreme cases.

How does hyperthyroidism increase metabolism?

Metabolism: Thyroid hormones stimulate diverse metabolic activities most tissues, leading to an increase in basal metabolic rate. One consequence of this activity is to increase body heat production, which seems to result, at least in part, from increased oxygen consumption and rates of ATP hydrolysis.