It is likely that all cells in the body are targets for thyroid hormones. Thyroid hormones have profound effects on many physiologic processes, such as development, growth, and metabolism. Thyroid hormones stimulate diverse metabolic activities in 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.