And it also increases the rate at which our heart actually contracts. So it influences this basal metabolic rate. Now, these hormones are actually also very important in the growth and the development of our organism from the child into an adult. Now, we have two important abnormalities that we should be familiar with when we're discussing T three and T four. We have something called hypothyroidism, and we have hyperthyroidism. So hypo simply means we have an insufficiency of.