 Hi, welcome to Nursing School Explained. Today's topic is the thyroid gland and how it regulates basic metabolic rate and therefore helps us process all the different functions in the body. We'll also be looking at hypo and hyperthyroidism. But first let's take a look at the basis of the thyroid gland. So I already mentioned that it regulates metabolic rate and we usually call this BMR, basic metabolic rate. And the follicular cells of the thyroid trap iodine that we consume in our diet and combine it to make T3 and T4. And remember the thyroid gland sits right here at the anterior neck area. So the thyroid gland functions by a negative feedback loop. And there are other glands in parts of the body that are involved in the balance of the thyroid hormones. So the thyroid hormones, the two thyroid hormones that we can measure in the bloodstream are T3 and T4, which is triiodothyroxine, so tri, meaning 3, T3, and then thyroxine, which is T4. But it all starts with the hypothalamus in the brain that releases thyroid releasing hormone and stimulates the anterior pituitary gland. The anterior pituitary gland in turn releases thyroid stimulating hormone and that hormone, TSH, stimulates the thyroid gland right here to make T3 and T4. And then T3 and T4 act on all the target organs in the body to regulate our temperature, our pulse, our blood pressure, our basic metabolic elements of the body. Then T3 and T4 get measured in the bloodstream and this is what we as clinicians can measure on a blood test, T3 and T4. And then depending on the levels, the hypothalamus will say, okay, now we have enough T3 and T4 available in the system to go back to normal or I need to release more TRH to get TSH to stimulate the thyroid to produce more or less of the T3 and 4. So it's a very nice feedback mechanism depending on the demands of the body at a time. Now when we look at, there is a continuum of thyroid dysfunction. So in the middle here we have normal. So this is when everything is in balance, all the metabolic mechanisms work as perfect as they can. And this is called u-throid. So remember u is always means normal or equal. And then we have along the continuum we have hyper and hypothyroidism. So hypothyroidism means that now the thyroid gland is producing too much T3 and T4. Remember we can measure the T3 and T4 and this is what we'll determine if the condition is hyper or hypothyroid. So when the condition is hyperthyroid, the thyroid simulating hormone will actually be low with an elevated T3 and T4. And the reason that that happens is because we have so much T3 and T4 circulating in the bloodstream that the hypothalamus says I don't need you pituitary to release this TSH because I know that I have a lot of T3 and T4 in the system and therefore everything kind of runs on super speed which we'll look into signs and symptoms of hyperthyroid later. Now when this gets really severe, when this gets so out of balance that the patient's hyperthyroidism gets even into a thyroid storm is what it's called and patients can't die from that. So because again metabolic rate is affected. On the other end of the spectrum we have hypothyroidism. Remember that we mostly look at T3 and T4 because that's what measures our ability to produce these thyroid hormones. And so in hypothyroidism, the thyroid does not produce the T3 and the T4. Therefore the pituitary and the hypothalamus say hello I need you to be producing T3 and 4 and continuously stimulate the thyroid gland with thyroid stimulating hormone. Therefore TSH will be high and T3 and T4 will be low. Now if this hypothyroidism gets really severe then the patient might go into a condition called mixed edema coma and that's the severe form of hypothyroidism and again patients can die from the severe form of basically uncontrolled basic metabolic rate and because all the functions basically just sees or don't function at all and therefore patients can go into a coma and can die.