Hyperthyroidism Overview (causes, pathophysiology)

hello in this video we're gonna talk about hyperthyroidism which is defined as elevated thyroid hormone levels and circulation thyroid hormones are very important in fetal development and also in metabolism so high levels of thyroid hormones in circulation as you can imagine will amp up metabolism to a point where it becomes pathological hyperthyroidism and thyrotoxicosis actually mean kind of the same thing however some define hyperthyroidism specifically to be increased synthesis of thyroid hormones in the thyroid gland whereas thyrotoxicosis refers to a clinical syndrome of excess circulating thyroid hormones irrespective of the source in this video hyperthyroidism will mean high levels of thyroid hormones in circulation causing the signs and symptoms of hyperthyroidism understanding the physiology of the thyroid gland the hypothalamic pituitary thyroid axis is important to understanding hyperthyroidism tired trope in releasing hormone trh stimulates the synthesis and secretion of thyroid stimulating hormone TSH which acts at the thyroid to stimulate all steps of thyroid hormone bio synthesis and secretion by binding onto thyroid stimulating hormone receptors the thyroid hormones are tired of Theron and t3 and thyroxine tea for these thyroid hormones control the secretion of trh and TSH by negative feedback to maintain the physiological levels of the main hormones of the hypothalamic pituitary thyroid axis in hyperthyroidism there's elevated circulating thyroid hormones which means there will be a negative feedback loop causing a decrease in trh and TSH the functional units of the thyroid glands are the follicles made up of follicular cells the center of the follicle is the colloid the thyroid gland has a rich blood supply and here the capillaries which will bring TSH thyroid stimulating hormones to these cells next to the follicles are the power of follicular cells also known as C cells which produce calcitonin another hormone which will not talk about but has an important role in calcium homeostasis zooming closer now at the interaction between the capillary and the follicle the capillaries of course brings thyroid stimulating hormone to the area the inner part of the follicle is a colloid Ascenta on the follicular cells you have thyroid stimulating hormone receptors when thyroid stimulating hormone reaches the thyroid follicular cells it binds to thyroid stimulating hormone receptors causing a number of things firstly it will stimulate thyroid globulin production thyroid globulin will enter the colloid thyroid globulin contains tyrosine groups which are important in making the thyroid hormones TSH also stimulates the expression of channels such as sodium iodide channels allowing circulating iodide to enter the follicular cells from here iodide enters the colloid via another channel and becomes oxidized to iodine iodine and thyroglobulin is what makes our thyroid hormones t3 and t4 t3 and t4 will enter circulation the thyroid hormones travel in circulation bound to proteins the main protein being thyroxine binding protein and here it will target the different cells around our body to elicit an effect so increasing metabolism in this video hyperthyroidism will mean high levels of thyroid hormones in circulation causing the signs and symptoms of hyperthyroidism causes of hyperthyroidism can be divided into two groups one group is where you have increased synthesis of thyroid hormones of whatever caused this group is called hyperthyroidism with normal or high Radio iodine uptake increased iodine uptake makes sense because increased Fired hormone synthesis requires an increase in iodine the other group is hyperthyroidism with near absent radio iodine uptake this means that hyperthyroidism is not a result of increased synthesis of thyroid hormones can you think of any if not just wait and we'll find out together let us first focus on hyperthyroidism where there is an increase in thyroid hormone synthesis production the autoimmune disorder Graves disease is the most common cause of hyperthyroidism the disease is much more common in women than in men and begins between ages 20 and 40 years in Graves disease there is a presence of autoantibodies against thyroid stimulating hormone receptor these antibodies stimulate and activate the thyroid stimulating hormone receptor activated thyroid stimulating hormone receptor as we have learned means increase in thyroid globulin and iodine in the colloid which means more t3 and t4 can be produced more t3 and t4 then enter circulation bound to proteins resulting in hyperthyroidism another cause of hyperthyroidism is toxic adenoma or toxic multinodular goiter in this case the nodules can be initially not toxic but through time they can undergo genetic mutations causing an abnormal thyroid stimulating hormone receptor the mutated third stimulating hormone receptor becomes autonomous it can activate by itself in the in the presence or in the absence of TSH this means more thyroid globulin more iodine in the colloid this means more t3 and t4 can be produced more t3 and t4 enter circulation resulting in hyperthyroidism another example although very rare is iodine excess we know that the normal process of TSH will stimulate the TSH receptor and we know that iodine is very important in the production of thyroid hormones if we have a lot of iodine this will of course shift production to the right more so we produce more thyroid hormones with more thyroid hormones means that we have hyperthyroidism a very interesting cause of hyperthyroidism is during early stages of pregnancy gestation when beta HCG the pregnancy hormone is produced by the fertilized egg at very high levels human chorionic gonadotropin the betta HCG or HCG not only interacts with its cognate receptors the luteinizing hormone receptors but it also cross reacts with thyroid stimulating hormone receptors this results in a physiological increase in thyroid hormone synthesis and a decrease in thyroid stimulating hormone levels in some women this mechanism can actually lead to overt hyperthyroidism during pregnancy autonomous secretion of thyroid stimulating hormone by a pituitary adenoma is a rare cause of hyperthyroidism the chirchi adenoma can be malignant or non-malignant regardless it causes an increase in thyroid stimulating hormone production with more third stimulating hormone in circulation this means the thyroid stimulating hormone receptor is stimulated activated thyroid stimulating hormone receptor increases thyroid globulin iodine in the colloid which means more to 3 and T 4 more t3 and t4 that enter circulation bound to protein resulting in hyperthyroidism the causes of hyperthyroidism we have discussed so far are all examples of an increase in thyroid hormone synthesis this is why these examples are categorized as hyperthyroidism with normal or high Radio iodine uptake because increase in thyroid hormone synthesis means more iodine needs to be taken up the other cause of hyperthyroidism is where there is near absent iodine uptake which means there is no actual increase in thyroid hormone synthesis in the thyroid gland a good example of this is ingestion of thyroid hormones either factitious ingestion of thyroid hormones or overdosing accidentally with the levothyroxine when you ingest thyroid hormones they are absorbed easily in the gut and can enter circulation easily causing hyperthyroidism this still has that negative feedback to the brain to reduce thyrotropin-releasing hormone and thyroid stimulating hormone levels an interesting cause of hyperthyroidism here in this group is called hamburger thyrotoxicosis probably not common now but back in the day when beef was being made some of the burgers contained the cow's thyroid glands because you're eating thyroid glands you probably are consuming all that stored thyroid hormone which will increase the thyroid hormone levels in the blood causing hyperthyroidism ectopic production of thyroid hormones from thyroid cancer metastases to other organs for example thyroid cancer metastases to the bones nearby is another cause this metastatic thyroid cancer can begin to produce thyroid hormones increasing thyroid hormone levels not sure why this is placed under the hyperthyroidism with near absent Radio iodine uptake because technically there is an increase in thyroid hormone synthesis anyway the final cause of hyperthyroidism with near absent radio iodine uptake is thyroiditis which is inflammation of the thyroid gland when you have inflammation of the thyroid gland you can imagine the follicular cells are destroyed releasing all its content into the bloodstream resulting in hyperthyroidism there are many causes of hyperthyroidism radiation medication lithium and infection and even autoimmune all these different types of thyroiditis have their own unique names which we will not go into so those are the causes of hyperthyroidism to summarize hyperthyroidism is we have excess amounts of t3 and t4 in circulation hyperthyroidism can be divided into hyperthyroidism with normal to high radio iodine uptake which means basically increase in thyroid synthesis in the thyroid gland or hyperthyroidism with near absent radioiodine uptake which basically means there's no synthesis of thyroid hormones from the thyroid gland

Channel: Armando Hasudungan

Views: 122,575

Rating: 4.9422259 out of 5

Keywords: Hyperthyroidism diet, Hyperthyroidism disease, Overactive thyroid, symptoms of hyperthyroidism, weight loss - topic, Thyroid disease in women, Endocrine system - topic, overactive thyroid symptoms, hyperthyroidism pathophysiology, causes of hyperthyroidism, treatment for hyperthyroidism, diet for hyperthyroidism, Hyperactive thyroid, thyroid gland hyperactive, Hyperthyroidism Disease, Hyperthyroidism medicine, Thyroid disease lecture

Id: Urwbo61a6Po

Length: 12min 7sec (727 seconds)

Published: Tue Jun 18 2019