Thyroid and Parathyroid

[Music] in this video we're going to look at the thyroid gland and the parathyroid gland okay so what is their function what hormones do they produce and how are they regulated so let's look at the thyroid gland first hey where's your thyroid gland located if you feel in your neck you have a bump that's sticking out that's your adam's apple or your larynx if you talk while you touch it you can feel it vibrating because that's where your voice box is your thyroid gland is sort of around and below your voice box the parathyroid glands there's four tiny parathyroid glands located on the posterior or the back side of your thyroid so the thyroid gland produces thyroid hormones they are t3 and t4 that is triodo thyronine and thyroxine and we will look at how those molecules are produced but first why are they produced what stimulates the production of our thyroid hormones okay do you remember the hypothalamus produces thyrotropin releasing hormone the hypothalamus that hormone then stimulates the anterior pituitary that will make thyroid stimulating hormone thyroid stimulating hormone stimulates the thyroid to make t3 and t4 now when does this occur how is it regulated okay the hypothalamus is regulated by negative feedback so when thyroid hormone levels go down the hypothalamus will be stimulated to make thyrotropin releasing hormone so the thyroid its general main overall function is in metabolism so whenever we need to have atp our energy we need to have more thyroid hormones so we will also stimulate the hypothalamus when we are exercising okay so exercise will stimulate through a cascade of events an increase in thyroid hormone production and then also acute stress responses will increase thyroid hormones because we need energy for stress now let's have a look at our thyroid anatomy so here is our larynx and we can see the thyroid gland is right here it's anterior to the trachea okay and you can feel your larynx and you can feel the rings of cartilage around your trachea and your thyroid gland might feel a bit like a little marshmallow around the front of your trachea okay it's a very highly vascular gland and if we took a little cross-section and looked inside the thyroid gland has these sort of large regions called colloid which are fluid filled sections that are surrounded by cells now the cells that surround these colloid regions there's two main types one of them is called follicular cells and the other type let's just shade it so it's a little different is called parafollicular cells now different hormones are made in each cell type the follicular cells are the ones that make the t3 and the t4 parafollicular cells make a hormone called calcitonin and this hormone is very important for calcium regulation we will talk about that next so first we will look at how the follicular cells produce t3 and t4 there are two minerals that are really important for thyroid hormone production okay the first one is iodine we need to have iodine in order to be able to make thyroid hormones if you're iodine deficient you will not be able to make thyroid hormones the other thing is we use the amino acid tyrosine and then the other mineral that we require is selenium selenium is a really important mineral for converting t4 into t3 t3 is the more active of the two thyroid hormones so if you don't have selenium to convert it you won't have enough active t3 so here we have our bloodstream we have a follicular cell and we have a colloid region in the follicular cell follicular cells have a nucleus with rough endoplasmic reticulum just like other cells and here we have our dna so there's genes in here and rough endoplasmic reticulum is for synthesizing proteins a very important protein that is produced is moved into the colloid and that is called thyroglobulin thyroglobulin uses the amino acid tyrosine to produce two molecules so tyrosine two tyrosine molecules will combine with iodine to produce a mono iodo tyrosine which has one iodine molecule or diodo tyrosine which has two iodine molecules so iodine has to be consumed in the diet as as an ion it will diffuse through into the follicular cell now it has to be carried by a membrane transporter protein and it is co-transported with sodium ions then the iodine once it is in the follicular cell it is transported through another membrane protein into the colloid now this mono ioto tyrosine and diioto tyrosine they can be combined to produce either t3 or two of these can produce t4 so mit and dit they will move back into the follicular cell through endocytosis and once they are in the follicular cell they are going to combine with a lysosome lysosomes contain digestive enzymes and it will cleave off the thyroglobulin molecule to produce rt3 and rt4 so t3 has one two three iodines and t4 has one two three four iodine molecules now remember that thyroid hormones even though they are made from amines they are fat soluble so when a hormone is fat soluble it can diffuse across a membrane but in order to be transported in the blood it will need a plasma protein to be able to travel through the blood so we know that thyroid hormones play a very important role in metabolism but there's a few other very key things that thyroid hormones do so let's look at this list thyroid hormones regulate fat carbohydrate and protein metabolism we can break down all of these nutrients to make energy carbohydrates in our body are stored in the liver and muscles as glycogen thyroid hormones tell the mitochondria to use oxygen to help us make atp in all cells including the brain so having low thyroid hormones would affect cognitive abilities like learning and thinking and being able to concentrate as well as mood thyroid hormones help us metabolize vitamins vitamins act as coenzymes in chemical reactions it stimulates the production of growth hormone and it has a synergistic effect with growth hormone so both of these combined are important for protein synthesis and for bone growth it increases the sensitivity to catecholamines catecholamines are dopamine epinephrine and norepinephrine they are also made from tyrosine but only one tyrosine molecule not two combined like thyroid hormones we increase the production of catecholamines when we have a stress response an autonomic sympathetic nervous system response so when we have stress so epinephrine for example increases heart rate and increases cardiac output and thyroid hormones increase that effect so if you had excess thyroid hormones you would have excess effects of a stress response so having more thyroid hormones can cause anxiety we will look at what happens when you have too much or too little thyroid hormones are very important for cell differentiation and development so during embryonic development it helps cells to become differentiated into specialized cells like liver cells and bone cells it has a very profound effect on brain development during fetal development and it affects body temperature when we produce atp a byproduct is heat so when our metabolism increases we make more heat and that helps us regulate our body temperature when our metabolism goes down we might feel a bit colder and this is why when we exercise we feel warmer and we start to sweat so now that you know the functions of the thyroid hormones think about how you would feel if you had too much or too little okay so when you have too much thyroid hormone is called hyperthyroidism when you have two low thyroid levels then it's hypothyroidism so with hyperthyroidism you're going to have symptoms like being excessively warm or heat intolerant you're going to have an increased heart rate increase breathing increase cardiac output you might have more of an appetite you might have sleeping problems insomnia anxiety irritability those kinds of symptoms whereas with hypothyroidism your metabolism is going to be lower so you can have weight gain you'll be fatigued you might feel depression you would have a difficult time concentrating be more forgetful not being able to focus on what you're doing um and also with low thyroid hormones dry flaky skin seems to be a common side effect and also hair loss can be related to low thyroid hormones so the point is that we need to have a balance with every single hormone too much or too little will cause symptoms and it will take you out of homeostasis we need to have the right amount of every hormone at the right time for the physiological situation for our cells to be able to function properly there's two autoimmune diseases that are becoming more and more prevalent in the population so one of them is called graves disease graves disease is an autoimmune disease where the immune system produces antibodies that bind to receptors that increase the production of thyroid hormones so graves disease stimulates the production and causes hyperthyroidism and hajimoto's disease is an autoimmune disease as well but the immune cells attack the thyroid cells so there is a hypothyroidism the other thing that i want to talk about is goiter goiter means that your thyroid gland is enlarged and sometimes it's very visible and you can see that the thyroid gland has grown and that is called hypertrophy so goiter can be caused by either hyper or hypothyroidism and that seems a little bit weird but i'm going to explain why so the anterior pituitary gland produces thyroid stimulating hormone tsh will stimulate the thyroid to produce thyroid hormones and it also can stimulate growth of the thyroid gland and increase the development of follicular cells so when the thyroid hormones are regulated when there's thyroid hormone it will inhibit the hypothalamus and that will inhibit the anterior pituitary now let's suppose you had hypothyroidism now you don't have enough t3 and t4 now the hypothalamus is going to keep increasing thyrotropin releasing hormone which will stimulate the pituitary to make more thyroid stimulating hormone trying to make the thyroid produce thyroid hormones so then that thyroid stimulating hormone will cause the thyroid gland to grow and that's a goiter so you can increase the thyroid gland size by having low thyroid hormones with hyperthyroidism when you have the increased stimulation so say in graves disease where you have antibodies that are stimulating the production of thyroid hormones that stimulation is increasing the size of the thyroid gland and you're getting more thyroid hormones so in both cases you can have a goiter now let's switch gears and look at the parathyroid hormone and then we'll go back to that calcitonin hormone that we talked about in the beginning so we are now going to look at calcium regulation blood calcium levels need to be highly regulated because it's very important for the nervous system for releasing neurotransmitters and very important for the muscular system for muscle contraction we need calcium to move the troponin and the tropomyosin so that the muscle fibers can contract so without calcium you can't contract muscles including your heart and your smooth muscles like muscles in your blood vessels so our body very highly specifically regulates blood calcium levels and it does that with two different hormones so the first one is parathyroid hormone and that is made by the parathyroid glands and that increases blood calcium levels when blood calcium levels are low and then calcitonin decreases blood calcium levels when blood calcium levels are too high so they balance each other so that we can always have the right amount of blood calcium levels so let's look at a bit more detail of how that works this diagram is showing the posterior side of our thyroid gland and you can see that we have these four parathyroid glands on the posterior side so each of these parathyroid glands has chief cells that produce parathyroid hormone now in this diagram we are looking at how homeostasis is maintained with our blood calcium levels let's suppose our blood calcium levels are decreasing that is going to stimulate the parathyroid gland parathyroid gland will make parathyroid hormone now it is going to increase blood calcium levels but how does it do it it basically has three targets so number one it is going to target the bones because the bones are a great reservoir of calcium in the bones we have osteoblast cells that build bone tissue and we have osteoclasts that break it down so the osteoclasts will break down bone and allow minerals to go into the bloodstream our skeleton is a really great source of stored minerals including phosphate and magnesium and others but we'll focus on calcium so when parathyroid hormone stimulates the bones it's going to stimulate the osteoclasts parathyroid hormone also stimulates the kidneys now the kidneys can excrete or reabsorb calcium so parathyroid hormone will tell the kidneys to reabsorb calcium so it stays in our body and we don't excrete it and then the last thing is it will convert vitamin d into an active form vitamin d is very important because it stimulates the digestive tract to absorb calcium so calcium is one of those minerals that we don't just absorb all the time if it's in your diet we only absorb it if vitamin d is activated and tells the intestine to absorb calcium so we release calcium from the bones we tell the kidneys to reabsorb calcium and we stimulate the production of active vitamin d so that we can absorb calcium from our small intestine from our diet all three of those things are going to cause our blood calcium levels to increase now over here let's suppose the stimulus was high blood calcium levels now we have too much blood calcium now what is going to happen then we will stimulate the thyroid gland the para follicular cells will produce calcitonin calcitonin has two primary targets one is the bones but now instead of stimulating the osteoclasts it's going to inhibit the osteoclasts so that more calcium isn't going into the bloodstream and then it will also stimulate the kidneys and it will decrease the amount of calcium that's taken up so more calcium will be excreted and then we will go back into homeostasis so parathyroid hormone will increase blood calcium and calcitonin will decrease blood calcium with blood calcium if we had a vitamin d deficiency if we were children with a vitamin d deficiency we would not have enough calcium to build bones properly and that can cause a disease so a vitamin d deficiency in children can cause rickets in adults a vitamin d deficiency can cause osteomalacia and that is where there's not enough bone mineralization but bones are kind of soft they still have collagen which makes them sort of flexible but they're still at an increased risk of having fractures and then the other disease that i want to mention is osteoporosis which can happen as we get older so osteoporosis is also a demineralization of the bones but the bones become brittle and more likely to fracture as well so in order to prevent osteoporosis we need a couple of things number one we need to have calcium in our diet so that when we stimulate vitamin d to become active vitamin d and we there has to be calcium to absorb in the digestive tract okay so if you're not consuming calcium then you're not going to be able to increase your blood calcium levels so then the calcium is just always going to come from the bones the other thing that we need is vitamin d so vitamin d tells the body to absorb the calcium from our diet and then the last factor that is important for preventing osteoporosis is exercise the bones have to be stimulated so even if you take calcium supplements if you're not exercising and stimulating the bones the bones won't take up that calcium and you will just excrete it and here is a summary chart of our thyroid hormones parathyroid and calcitonin you

Channel: Dr. Wendi

Views: 5,624

Keywords: Thyroid, parathyroid, T3, T4, iodine, follicular cells, calcitonin, Grave's, Hashimoto's, Calcium regulation, metabolism, hyperthyroidism, hypothyroidism, vitamin D, Fanshawe College, Prehealth, Biology, Physiology, osteoporosis, Rickets, Osteomalacia

Id: oZtm2nv5DPM

Length: 21min 8sec (1268 seconds)

Published: Fri Sep 18 2020