Thyroid hormones affect almost every cell in the body. Some important effects of thyroid hormones on various cells and organ systems are:

• Increases body metabolism by increasing the rate at which cells use oxygen and food to produce energy

• Causes the cardiovascular system to be more sensitive to sympathetic nervous activity

• Increases heart rate and force of contraction of heart muscle

• Maintains normal sensitivity of respiratory centers to changes in oxygen and carbon dioxide concentrations

• Stimulates the formation of red blood cells to enhance oxygen delivery

• Stimulates the activity of other endocrine tissues

• Ensures proper skeletal development in children