Pathophysiology: There is a reduction in thyroid hormone secretion. This is caused by an autoimmune disorder attacking the thyroid and causing this reduction.
- Hyposecretion of thyroid hormone
- Results in a decreased metabolic rate
- Hashimoto’s Thyroiditis
- Iodine Deficiency
- Myxedema Coma
- Acute Exacerbation
- Life-threatening state of decreased thyroid production
- Caused by acute illness, rapid cessation of medication, hypothermia
- Hypometabolic state
- Goiter – enlarged thyroid due to iodine deficiency
- ↓ T3, T4, Free T4 hormones
- ↑ TSH levels
- Bradycardia, hypotension
- Lethargy, fatigue, weakness
- Muscle aches
- Dry skin
- Loss of body hair
- Cold intolerance
- Weight gain
- Medication Therapy
- Levothyroxine (Synthroid)
- Monitor – possible overdose
- Cardiac Monitoring
- Maintain open airway, especially with goiter
- Have tracheotomy supplies available
- IV fluids to support hemodynamics
- Administer glucose/dextrose as needed
- Encourage nutrition intake
- Assess thyroid hormone levels
- Hormone Regulation
- Administer medications (levothyroxine)
- Monitor hormone levels (T3, T4, Free T4, TSH)
- Monitor for s/s Myxedema Coma
- Keep warm
- Monitor temperature
- Ensure adequate nutritional intake
- Daily weights
- Do not stop taking medications without discussing with your provider
- Smoking Cessation
- Routine testing of TSH levels
- s/s to report to provider
- Could experience hyperthyroid if overdosing medications
- Myxedema coma
In this lesson we’re going to talk about hypothyroidism. You can already start to guess what this is by the name. Hypo always means low or not enough, and obviously we’re referring to the thyroid gland.
So, hypothyroidism is a condition of decreased secretion of thyroid hormones, so we’ll see decreased levels of T3, T4, and Free T4 in the blood. We’ll also see increased levels of TSH, or Thyroid Stimulating Hormone. Why is that? Well, let’s review how these hormones get secreted. The hypothalamus in the brain releases Thyrotropin Releasing Hormone, which goes to the pituitary gland and tells it to release Thyroid Stimulating Hormone. TSH goes to the Thyroid gland to tell it to secrete more thyroid hormones. Then, when the levels are high enough, the body sends a signal back to the hypothalamus to tell it to stop. That’s called a negative feedback loop. So, when something happens that causes these levels to be super low, that means TSH secretion will increased significantly. Now, there are multiple possible causes like Hashimoto’s Thyroiditis, which is an autoimmune disease, Iodine deficiency because those hormones are made from iodine – if I don’t have enough, I can’t make the hormones. But also if the patient has their thyroid removed altogether, that will cause hypothyroidism. So, what does this do? Well…it’s decreased thyroid hormone action. The thyroid hormones are responsible for increased metabolism, growth & development, and increased effect of catecholamines like epinephrine. But, the biggest thing we see is a decreased or slowed metabolic rate.
Now ANY time you think hypothyroidism I want you to think Hypometabolic. Everything is low or slow. It’s like a sloth, things are happening, just VERY slowly, and that can cause a lot of problems. They could have a low temperature and a cold intolerance – I mean think if you were already freezing and someone touches you with a cold bottle of water, you’re gonna freak out right? Since their metabolism is super slow, they’ll see some weight gain, some of which is from peripheral edema. They’ll likely lose their appetite because their gut isn’t moving like it should, and their blood sugar may even be low because of the body’s decreased ability to break down glycogen. In the cardiovascular system we’ll see bradycardia, hypotension, and anemia – again – low and slow. When the gut slows down we start to see serious constipation. It’s also possible to have nausea and even vomiting because of decreased gastric motility. And then, just like we saw in hyperthyroidism, we’ll see the goiter – except this time it’s due to the iodine deficiency. Usually other chemicals come together with the iodine to make the hormones, but they can’t without iodine, so they just build up in the thyroid – causing this goiter. So BOTH hyper and hypothyroidism will have a goiter – just for slightly different reasons. So you have to look at the REST of the clinical picture to understand what’s going on.
Other body systems will be affected, too – in the neurological system we’ll see lethargy, fatigue, muscle aches and weakness, and paresthesias – low and slow nerve impulses, right? Their skin will be dry and pale and they might have puffy eyes and a loss of body hair. Sometimes they will even have this blank expression on their face because of how weak the muscles are – you can see this gentleman has the pale skin, puffy eyes, and expressionless face. Then, as with most diseases, there’s a possibility for acute exacerbation, in this case known as Myxedema Coma. It’s a life threatening condition in which their heart rate and blood pressure dip dangerously low and they can slip into a coma. It can be due to acute illness, or hypothermia, but also if they abruptly stop their medication – so we NEED to teach our patients not to stop their meds without talking to their doctor first.
So when we’re managing hypothyroid patients, we can do a radionuclide scan with radioactive iodine and we’ll see decreased uptake. You can see how this thyroid isn’t very dark – if you watch the hyperthyroid lesson, you’ll see how it looks when it’s fully uptaking that iodine. So if they are hypothyroid and we see decreased uptake, decreased thyroid hormone levels, increased TSH levels, we’ll put them on hormone replacement therapy with levothyroxine or Synthroid. We just want to monitor them closely because we don’t want to overdose them and send them into a thyroid crisis. It all needs to be balanced well. Of course we’re going to monitor their heart and give IV fluids to support their blood pressure. We also need to make sure we maintain an open airway. We are always concerned about this with goiter and thyroid swelling and may consider having tracheotomy supplies available just in case. Since they’re at risk for hypoglycemia and anorexia, we want to monitor blood sugars and give dextrose as needed and encourage good nutritional intake. It’s hard to encourage someone to eat more or better when they’re gaining weight because their metabolism is so slow. We just need to educate them about how important good nutrition is, and to trust the medication.
Our priority nursing concepts for patients with hypothyroidism are going to be hormone regulation, thermoregulation, and nutrition. With that hypometabolic state we really need to make sure they’re getting high quality nutritional intake, and taking their meds appropriately, and we’re monitoring for and preventing Myxedema Coma. Make sure you check out the care plan attached to this lesson for more detailed nursing interventions and rationales.
So, let’s recap. Hypothyroidism is a state of decreased secretion of thyroid hormones, so we see decreased T3, T4, and free T4 levels and increased TSH levels. It could be caused by Hashimoto’s Thyroiditis, iodine deficiency, or removal of the thyroid altogether. Remember when you think hypothyroid, I want you to think hypometabolic. Their blood pressure, heart rate, and temperature all go down and they might even be weak and fatigued. We want to give levothyroxine to increase their hormone levels and monitor those levels closely so we can prevent the risk of Myxedema Coma or Thyroid Storm.
So those are the basics of hypothyroidism, we’ve created a cheatsheet to help you learn the difference between hyper and hypothyroid so make sure you check that out. Now, go out and be your best selves today. And, as always, happy nursing!