Med-Surg Endocrine System, part 14: Hypothyroidism & Myxedema Coma

by Cathy Parkes August 01, 2020

Full Transcript

Alright. In this video, we are going to talk about hypothyroidism and myxedema coma. If you are following along with cards, I'm on card 34. So with hypothyroidism, we have inadequate production of T3 and T4 which are thyroid hormones in the thyroid gland. In terms of the pathophysiology behind hypothyroidism, causes could include primary, secondary, or tertiary causes. So, just to do a little review here, the hypothalamus produces thyroid-releasing hormone TRH, which causes the pituitary gland to produce TSH or thyroid-stimulating hormone, and that allows the thyroid gland to produce T3 and T4. So with primary hypothyroidism, that's where we have an issue with the thyroid gland itself. So the leading cause of primary hypothyroidism is Hashimoto's disease which is an autoimmune disorder that causes antibodies to attack and destroy the thyroid tissue. So if the thyroid gland is damaged, it can't produce its T3 and T4 like it should. Secondary causes of hypothyroidism is where we have an issue with the pituitary gland, like if there was a pituitary tumor. This decreases production of TSH so the thyroid gland is not getting the message it needs to produce T3 or T4. And then we have tertiary causes of hypothyroidism. So if there is some kind of dysfunction in the hypothalamus then the hypothalamus is not releasing TRH and therefore, the pituitary gland is not releasing TSH, and that is causing inadequate production of T3 and T4. So hopefully that's helpful for you to be able to differentiate the three different causes of hypothyroidism.

Alright. Now, let's talk about the signs and symptoms of hypothyroidism. This includes hypotension, bradycardia, lethargy, cold intolerance, constipation, weight gain, thin hair, brittle fingernails, as well as depression. In terms of what labs we may see, it really depends on whether we're dealing with primary hypothyroidism or secondary or tertiary hypothyroidism. So with primary hypothyroidism, we have an issue in the thyroid gland itself. So it's been injured, and it's just not able to produce that T3 and T4. However, the pituitary gland is working just fine. So the pituitary gland is desperate to try to get this thyroid gland to produce its T3 and T4. So it's increasing levels of TSH. Be like, "Come on thyroid gland. Here's more TSH. Can you please get going on making your T3 and T4?" And the thyroid gland like, "Sorry, dude. I'm injured. I'm going to chill out. I can't produce any T3 or T4." So labs that you would see with primary hypothyroidism include low levels of T3 and T4 but elevated levels of TSH. On the other hand, if you're dealing with secondary or tertiary hypothyroidism, this means that the thyroid gland itself is working fine but it's not getting the right signal from the pituitary gland. So the pituitary gland is not producing enough TSH and that makes the thyroid gland not produce T3 and T4. So if you look at the labs for secondary hypothyroidism, you're going to have low levels of T3 and T4 but you're also going to have low levels of TSH because there's some kind of pituitary tumor or the pituitary gland is not getting the proper signal from the hypothalamus. If there's a problem with the hypothalamus, that causes decreased TRH, which causes decreased TSH, which causes decreased T3 and T4. Okay? So those are the labs you can expect. Over the years, I've had periods of time where I was feeling like, "Oh, I'm really tired and I'm cold all the time and I've kind of gained some weight. And maybe I have hypothyroidism." And I go and I get that checked out and all the time, my T3, T4, and TSH levels are all normal. So that has never been the problem. It's like, well, maybe I just need to stop eating so much and exercise more. That might work too. So I've never actually had any issues with my thyroid, but I've always suspected that I may have had those issues in the past.

Okay. In terms of treatment, we would give them a synthetic form of the thyroid hormones. So this would include levothyroxine or liothyroxine. So you would give this medication not with meals - so like an hour before meals - in the morning with a full glass of water. So at the hospital, they always schedule thyroid medications, levothyroxine or liothyroxine, at 6:00 AM. So you get to wake your patient up at 6:00 AM and give them their thyroid medication with a full glass of water. And, boy, are they happy to see you at 6:00 AM. Not. So a lot of times, if they have to have labs in the morning, I try to coordinate it all so they get their labs drawn, we could do their vital signs, and they get their thyroid medication all at once, so then I can leave them alone after that.

Okay. In terms of nursing care for a patient who has hypothyroidism, you want to encourage frequent rest periods because they have this lethargy, you want to encourage a low-calorie, high-fiber diet to help promote weight loss and to prevent constipation, and then you want to increase the patient's room temperature and provide blankets because they have this cold intolerance.

Okay, finally let's talk about myxedema coma, which is one of our critical care topics here in the Medical-Surgical Deck, Card 36. So this is where we have a patient with severe, life-threatening hypothyroidism, and it could be due to the fact that they have untreated hypothyroidism, or they may have abruptly discontinued their thyroid medication, or it could be due to infection or illness. So signs and symptoms are very serious and include hypoxia as well as decreased cardiac output, decreased level of consciousness, bradycardia, hypotension and hypothermia. So in terms of the nursing care priorities, we're going to want to maintain a patent airway, right? So our ABC priorities, airway is most important. There's a chance that this patient will need to be intubated and receive mechanical ventilation, so you're going to want to assist with that. You're definitely going to want to monitor the patient's cardiac rhythm and administer large doses of thyroid medications such as levothyroxine as ordered. And then warm the patient as they will have hypothermia with this condition.

Okay, that is it for hypothyroidism and in my next video, we will talk about hyperthyroidism. Thanks so much for watching, and if this information has been helpful, be sure to like this video and leave us a comment. Take care, and good luck studying!

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