Hyperthyroidism & Hypothyroidism

This week, the most high-yield topic is hyper and hypothyroidism. You’ll see a lot of your test questions coming from this subject.

I’m gonna talk about hyperthyroidism first, and then I’ll cover hypothyroidism.

So, What is hyperthyroidism? It’s when your body makes too much of the thyroid hormones T3 and T4. I’m not sure how much of the A&P you remember from forever ago, so to review how T3 & T4 are made, your hypothalamus in your brain releases Thyroid Releasing Hormone; this makes the Pituitary gland release TSH, or Thyroid Stimulating Hormone, and that makes the thyroid, the little butterfly-shaped gland on your neck, produce T3 and T4.

In both hyper and hypothyroidism, the main causes are autoimmune disorders. The autoimmune disorder that causes hyperthyroidism is called Graves disease. With Graves disease, the patient will have a goiter, or an enlarged thyroid gland, that’s sometimes so big, you can see it from the door of their room. They’ll also have the characteristic bulging eyes, or exophthalmos. This will also be very noticeable, cause it’ll look like they are staring at you in a creepy way, and their eyes are protruding out of the sockets. Usually, our upper eyelids cover the top half of our iris. But in a patient with exophthalmos, you’ll be able to see the white of their eyeball above their iris, below their upper eyelid. So, if the patient has green eyes, you’d be able to see some white between the green and their upper eyelid. Sometimes the exophthalmos will be so bad that they can’t even close their eyelids all the way.

Hypothyroidism is when the thyroid gland doesn’t make enough T3 and T4. So just the opposite of hyperthyroidism. The most common cause is the autoimmune disorder, Hashimoto’s thyroiditis. I remember that Hashimoto’s causes hypothyroidism like hypO, HashimOto. Hashimotos is when your body makes antibodies that destroy your thyroid gland, which decreases T3 and T4. This causes the gland to grow bigger to compensate, which creates a goiter. So you can have a goiter with both hyper and hypothyroidism.

Another cause of hypothyroidism is simply not getting enough iodine in your diet, but this isn’t an issue here in the US, because we put iodine into our salt.

Also, if someone is getting treated for hyperthyroidism, like they get a thyroidectomy, or radioactive iodine ablation, those can both overcorrect to lead to hypothyroidism. Even if they are just taking antithyroid medication, and they take too much.