hi this is tom from zero to finals calm in this video I'm going to be talking about hypothyroidism you can find written notes on this topic at zero da finals comm slash hypothyroidism or in the endocrinology section of the zero to finals Medicine book let's jump straight in hyperthyroidism is the term used to describe inadequate output of thyroid hormones by the thyroid gland there's a few different causes the most common cause of hyperthyroidism in the developed world is Hashimoto's thyroiditis and this is caused by autoimmune inflammation of the thyroid gland so the body's immune system attacking the thyroid gland it's associated with anti-thyroid peroxidase or anti TPO antibodies and also with anti thyroid globulin antibodies initially it causes a bit of a goiter after which there's atrophy of the thyroid gland as the hyperthyroidism sets in iodine deficiency is the most common cause of hyperthyroidism in the developing world and this is because iodine is essential for the production of thyroid hormones iodine is added to foods like table salt to prevent iodine deficiency and to prevent hypothyroidism hyperthyroidism can also occur as a result of treatment for hyperthyroidism so all the treatments for hyperthyroidism have the potential to overshoot and cause hypothyroidism so these are treatments like kaboom azole propath io uracil radioactive iodine and of course thyroid surgery there are also medications that can cause hyperthyroidism lithium inhibits the production of thyroid hormones in the thyroid gland and so can cause a goiter and hypothyroidism amiodarone interferes with the thyroid hormone production and metabolism and usually it causes a hyperthyroidism but it can also cause a thorough toxicosis there's also secondary causes of hyperthyroidism or central causes and this is where the pituitary gland is failing to produce enough TSH and this is often associated with a lack of other pituitary hormones as well such as ACTH and this is called hypopituitarism and it has quite a few different causes and these causes can be tumors of the pituitary gland infections in that area vascular pathology such as something called Sheehan syndrome where you get pituitary necrosis after massive blood loss during child and radiation therapy to the pituitary gland so how do patients with hypothyroidism present well they can present with weight gain fatigue dry skin coarse hair and hair loss they can have fluid retention so they can develop a Deemer or pleural effusions or ascites they can have amenorrhea so the periods stop and it can slow down the bowels and make the very constipated so when you suspect hypothyroidism how do you investigate them well firstly you would do a TSH find that the TSH is abnormal and then do t3 and t4 levels in primary hypothyroidism this is caused by a thyroid gland insufficiency so the thyroid hormones like t3 and t4 will be low and the TSH level will be high because there's no negative feedback to the pituitary gland so the Petrucci produces lots of TSH to try and get the thyroid working again in secondary hypothyroidism it's caused by pituitary pathology and that results in a low production of TSH so TSH will be low and the thyroid hormones will be low how do we manage hypothyroidism well it's quite straightforward we simply replace the thyroid hormone that isn't there with oral lever thyroxine so we give them oral thyroid hormone in the form of levothyroxine levothyroxine is synthetic t4 and it metabolizes in the body to t3 so you get t4 and t3 from this one medication the doses are titrated until TSH levels are normal so when you start lever thyroxine initially measure the TSH levels monthly until the TSH level is stable and then once stable it can be checked less frequently unless the patient becomes symptomatic so if the TSH level is high you know the dose of levothyroxine is too low so it needs to be increased and if the TSH level is low you know that the dose of levothyroxine is too high and it needs to be reduced so thanks for watching I hope you found this video helpful if you did don't forget there's plenty of other resources on the zero to finals website including loads and loads of notes on various different topics that you might cover in medical school with specially made illustrations there's also a whole test section where you can find loads of questions to test your knowledge and see where you're up to in preparation for your exams there's also a blog where I share a lot of my ideas about a career in medicine and tips on how to have success as a doctor and if you want to help me out on YouTube you can always leave me a thumbs up give me a comment or even subscribe to the channel so that you can find out when the next videos are coming out so I'll see you again soon