Hashimoto thyroiditis

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Hashimoto thyroiditis

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USMLE® Step 1 style questions USMLE

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An 18-year-old woman comes to the clinic due to upper neck and jaw pain that started gradually a week ago. The patient is generally healthy, and medical history is unremarkable other than dysmenorrhea, for which she takes acetaminophen. Two weeks ago, she had an upper respiratory infection that resolved without treatment. During the past week, she has noticed that she sweats more than usual and has difficulty sleeping. Temperature is 37.0°C (98.6°F), pulse is 110/min, and blood pressure is 125/85 mmHg. On physical examination, the thyroid gland is diffusely enlarged and very sensitive to touch. Laboratory tests are obtained and reveal the following:


Radioactive iodine uptake test is performed and reveals diffusely decreased uptake. Which of the following is most likely involved in the pathogenesis of this patient’s condition?

External References

First Aid

2024

2023

2022

2021

Hashimoto thyroiditis p. 345

autoantibody p. 113

cholangitis association p. 402

goiter causes p. 346

HLA subtypes with p. 98

lymphoma association p. 347

Non-Hodgkin lymphoma p. 434, 435

Hashimoto thyroiditis and p. 345

Transcript

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Hashimoto’s thyroiditis, named after the Japanese physician Hakaru Hashimoto who first described it, belongs to a group of disorders where there’s some form of inflammation “-itis” of the thyroid gland.

It’s basically an autoimmune destruction of the thyroid gland, which typically progresses gradually to hypothyroidism, or state of too low “hypo-“ thyroid hormones.

In fact, Hashimoto’s thyroiditis is the most common cause of hypothyroidism in areas of the world where dietary iodine, the basic structural element of thyroid hormones, is sufficient.

Normally, the hypothalamus, which is located at the base of the brain, secretes thyrotropin-releasing hormone, or ΤRH, into the hypophyseal portal system - which is a network of capillaries linking the hypothalamus to the anterior pituitary.

The anterior pituitary then releases a hormone of its own, called thyroid-stimulating hormone, thyrotropin or simply TSH.

TSH stimulates the thyroid gland which is a gland located in the neck that looks like two thumbs hooked together in the shape of a “V”.

If we zoom into the thyroid gland, we’ll find thousands of follicles, which are small hollow spheres whose walls are lined with follicular cells, and are separated by a small amount of connective tissue.

Follicular cells convert thyroglobulin, a protein found in follicles, into two iodine-containing hormones, triiodothyronine or T3, and thyroxine or T4.

Once released from the thyroid gland, these hormones enter the blood and bind to circulating plasma proteins.

Only a small amount of T3 and T4 will travel unbound in the blood, and these two hormones get picked up by nearly every cell in the body.

Once inside the cell T4 is mostly converted into T3, and it can exert its effect. T3 speeds up the basal metabolic rate.

So as an example, they might produce more proteins and burn up more energy in the form of sugars and fats. It’s as if the cells are in a bit of frenzy.

T3 increases cardiac output, stimulates bone resorption - thinning out the bones, and activates the sympathetic nervous system, the part of the nervous system responsible for our ‘fight-or-flight’ response.

Summary

Hashimoto thyroiditis is a type of autoimmune disease that attacks and destroys the thyroid gland. This can cause hypothyroidism, which can lead to a wide range of symptoms, such as tiredness, weight gain, depression, and changes in your menstrual cycle. The cause of hashimoto's thyroiditis is unknown, but it's thought to be caused by a combination of genetic and environmental factors.

Sources

  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Harrison's Endocrinology, 4E" McGraw-Hill Education / Medical (2016)
  6. "Immune Disorders in Hashimoto’s Thyroiditis: What Do We Know So Far?" Journal of Immunology Research (2015)
  7. "Hashimoto’s Thyroiditis: History and Future Outlook" Hormones (2013)
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