Hypothyroidism and Hashimoto's Thyroiditis: Visual Explanation for Students

A clear visual explanation of hypothyroidism and Hashimoto's thyroiditis, covering causes, symptoms, diagnosis, and treatment with levothyroxine.

Key Takeaways

Hashimoto's thyroiditis is the most common cause of hypothyroidism in developed countries.
Iodine deficiency remains the main cause in developing countries and is preventable by iodized salt.
Medications and treatments for hyperthyroidism can induce hypothyroidism.
Diagnosis requires thyroid function tests focusing on TSH, T3, and T4 levels.
Levothyroxine is the standard treatment, providing synthetic T4 that converts to T3 in the body.

What the video covers

Hypothyroidism is caused by inadequate thyroid hormone output, most commonly due to Hashimoto's thyroiditis in developed countries.
Hashimoto's thyroiditis is an autoimmune inflammation of the thyroid gland associated with anti-TPO and anti-thyroid globulin antibodies.
Iodine deficiency is the leading cause of hypothyroidism in developing countries, with iodine added to salt to prevent it.
Hypothyroidism can result from treatments for hyperthyroidism or medications like lithium and amiodarone.
Secondary hypothyroidism arises from pituitary gland failure to produce enough TSH, often due to tumors, infections, or Sheehan syndrome.
Symptoms include weight gain, fatigue, dry skin, hair loss, fluid retention, amenorrhea, and constipation.
Diagnosis involves measuring TSH, T3, and T4 levels, differentiating primary (high TSH, low T3/T4) from secondary hypothyroidism (low TSH, low T3/T4).
Management involves thyroid hormone replacement with oral levothyroxine, titrated to normalize TSH levels.

Chapters

What is the most common cause of hypothyroidism in developed countries?

The most common cause is Hashimoto's thyroiditis, an autoimmune inflammation of the thyroid gland associated with anti-thyroid antibodies.

How is hypothyroidism diagnosed?

Diagnosis involves measuring TSH, T3, and T4 levels. Primary hypothyroidism shows high TSH and low T3/T4, while secondary hypothyroidism shows low TSH and low T3/T4.

What is the standard treatment for hypothyroidism?

Hypothyroidism is treated with oral levothyroxine, a synthetic T4 hormone that converts to T3 in the body, with doses adjusted to normalize TSH levels.

Full Transcript — Download SRT & Markdown

Speaker A

Hi, this is Tom from Zero to Finals.com. In this video, I'm going to be talking about hypothyroidism. You can find written notes on this topic at Zero to Finals.com/hypothyroidism or in the endocrinology section of the Zero to Finals Medicine book. Let's jump straight in.

Speaker A

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

Speaker A

Hypothyroidism 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 hypothyroidism 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 hypothyroidism sets in.

Speaker A

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

Speaker A

Iodine deficiency is the most common cause of hypothyroidism 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.

Speaker A

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

Speaker A

Hypothyroidism can also occur as a result of treatment for hyperthyroidism, so all the treatments for hyperthyroidism have the potential to overshoot and cause hypothyroidism. These are treatments like carbimazole, propylthiouracil, radioactive iodine, and of course thyroid surgery.

Speaker A

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

Speaker A

There are also medications that can cause hypothyroidism. 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 hypothyroidism, but it can also cause thyrotoxicosis.

Speaker A

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

Speaker A

There's also secondary causes of hypothyroidism, or central causes, and this is where the pituitary gland is failing to produce enough TSH. This is often associated with a lack of other pituitary hormones as well, such as ACTH, and this is called hypopituitarism. 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 childbirth, and radiation therapy to the pituitary gland.

Speaker A

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

Speaker A

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 edema or pleural effusions or ascites. They can have amenorrhea, so the periods stop, and it can slow down the bowels and make them very constipated.

Speaker A

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

Speaker A

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 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 pituitary produces lots of TSH to try and get the thyroid working again.

Speaker A

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

Speaker A

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.

Speaker A

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

Speaker A

How do we manage hypothyroidism? Well, it's quite straightforward. We simply replace the thyroid hormone that isn't there with oral levothyroxine, 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.

Speaker A

I'll see you again soon

Topics:hypothyroidismHashimoto's thyroiditisthyroid hormonelevothyroxineTSHT3T4iodine deficiencypituitary glandautoimmune thyroiditis

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