Pharmacology · chapter 27 · Thyroid and Parathyroid Disorder Drugs
Introduction to the Thyroid and Parathyroid
The 14 things this section of the textbook says that you are most likely to be asked about — quoted word for word, not retold. Then 6 practice questions with the reasoning.
Key points
The thyroid needs iodine
This important gland regulates metabolism in the body through the production and secretion of thyroid hormones, which require iodine for synthesis.
Calcitonin lowers blood calcium
Calcitonin lowers the levels of calcium in the blood by inhibiting the activity of osteoclasts—cells that break down bone tissue and release calcium into the blood.
Parathyroid hormone and calcium balance
The parathyroid glands secrete parathyroid hormone (PTH), which along with dihydroxy-vitamin D 3 (vitamin D 3) and calcitonin are responsible for calcium homeostasis within the body.
Negative feedback on thyroid hormones
Conversely, in cases where an excess of thyroid hormones is present, a crucial negative feedback system comes into play. Excessive levels of T4 and T3 instruct the anterior pituitary and hypothalamus to restrain the release of their respective hormones.
Hashimoto thyroiditis
Hashimoto thyroiditis is the most common cause of hypothyroidism. This condition is caused by an autoimmune-mediated destruction of the thyroid gland, which leads to a dysfunctional thyroid gland and decreased secretion of thyroid hormones.
Myxedema coma
If hypothyroidism is left untreated, the client may develop a myxedema coma, which is a life-threatening disorder that leads to hypothermia, cardiovascular collapse, hypoventilation, hyponatremia, hypoglycemia, lactic acidosis, and coma.
Slow heart rate in hypothyroidism
However, in hypothyroidism, the reduced levels of thyroid hormone cause the heart rate to decrease.
Graves' disease
The autoimmune disorder Graves’ disease is the most common cause of hyperthyroidism. In Graves’ disease, the production of TSH receptor antibodies stimulate the thyroid gland to grow and secrete additional thyroid hormone.
Thyroid storm
Thyroid storm (thyrotoxic crisis) is a rare but severe complication of hyperthyroidism, which leads to severe tachycardia, fever, dehydration, heart failure, and coma. It occurs in clients who are inadequately treated for hyperthyroidism or initially after the removal of the thyroid.
Weight loss despite appetite
This can lead to unintended weight loss, even with a normal or increased appetite.
Low PTH means low calcium
Hypoparathyroidism occurs when the body does not secrete enough PTH in the blood. This leads to dangerously low levels of calcium in the blood. Because calcium and phosphate have an inverse reaction, the phosphate levels in the body increase.
Causes of hypoparathyroidism
Hypoparathyroidism is typically caused by an autoimmune disorder, can be idiopathic, or is a result of thyroid/parathyroid surgery.
Treating hypoparathyroidism
Treatment for hypoparathyroidism includes intravenous calcium gluconate, oral calcium, and vitamin D supplements, which will be discussed later in this chapter.
Kidney stones in hyperparathyroidism
Increased levels of calcium in the blood due to hyperparathyroidism can lead to the deposition of calcium crystals in the kidneys, leading to the development of kidney stones.
Terms to know
- Chvostek sign
- Symptoms of hypoparathyroidism are tetany, contraction of facial muscles after tapping the facial nerve (Chvostek sign), induction of carpal pedal spasm (Trousseau sign), paresthesia, and a prolonged QT wave (total time from ventricular depolarization to complete repolarization) on an electrocardiogram.
- Hyperthyroidism
- Hyperthyroidism occurs when the body secretes too much T3 and T4 into the blood.
- Hyperparathyroidism
- Hyperparathyroidism occurs when the body secretes too much PTH in the blood, leading to dangerously elevated levels of calcium in the blood.
Practice questions
Stuck on select-all-that-apply? How to take them one option at a time.
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Every question here, with the answer
A client had a thyroidectomy yesterday. When the nurse taps in front of the ear, the client's facial muscles twitch. What does the nurse suspect?
- Hyperthyroidism
- Hypoparathyroidism with low calcium
- Myxedema coma
- Hyperparathyroidism
Answer: Hypoparathyroidism with low calcium
Contraction of facial muscles after tapping the facial nerve is the Chvostek sign, a symptom of hypoparathyroidism, which can result from thyroid or parathyroid surgery and causes low calcium. The other conditions do not produce this sign.
A nurse is assessing a client with suspected hypothyroidism. Which findings are consistent with it? Select all that apply.
- Bradycardia
- Cold intolerance
- Fine hand tremors
- Weight gain
- Constipation
Answer: Bradycardia, Cold intolerance, Weight gain, Constipation
Hypothyroidism slows the heart rate, reduces heat production, slows gut motility, and slows metabolism, causing weight gain. Fine tremors come from nervous system excitability in hyperthyroidism.
A client with poorly treated hyperthyroidism arrives with a heart rate of 150, fever, and dehydration. Which complication should the nurse suspect?
- Thyroid storm
- Myxedema coma
- Hypoparathyroidism
- Hashimoto thyroiditis
Answer: Thyroid storm
Thyroid storm is a severe complication of hyperthyroidism that causes severe tachycardia, fever, dehydration, heart failure, and coma, often in inadequately treated clients. Myxedema coma comes from untreated hypothyroidism with hypothermia.
Lab results show TSH low, T4 high, and T3 high. Which condition do these results indicate?
- Hypoparathyroidism
- Hyperthyroidism
- Normal thyroid function
- Hypothyroidism
Answer: Hyperthyroidism
Excess T4 and T3 suppress TSH through negative feedback, so low TSH with high T4 and T3 indicates hyperthyroidism. Hypothyroidism shows high TSH with low T4 and T3.
A client has hyperparathyroidism. Which findings should the nurse expect? Select all that apply.
- Elevated serum phosphate
- Kidney stones
- Polyuria
- Constipation
- Bone pain
Answer: Kidney stones, Polyuria, Constipation, Bone pain
High PTH raises calcium, causing kidney stones, constipation, bone pain, and polyuria. Because calcium and phosphate move inversely, phosphate falls rather than rises.
A client with untreated hypothyroidism becomes hypothermic, hypoventilates, and is difficult to arouse. What should the nurse recognize?
- Possible myxedema coma, a life-threatening emergency
- Normal response to cold weather
- Thyroid storm
- Expected fatigue from hypothyroidism
Answer: Possible myxedema coma, a life-threatening emergency
Untreated hypothyroidism can progress to myxedema coma, which causes hypothermia, hypoventilation, and coma and is life-threatening. Thyroid storm presents with fever and tachycardia instead.
Where every quote comes from
Section 27.1 Introduction to the Thyroid and Parathyroid of Pharmacology for Nurses by Tina Barbour-Taylor, Leah Mueller (Sabato), Donna Paris, Dorie Weaver, OpenStax, 2024. Read the whole section free at openstax.org.
The textbook is licensed under CC BY-NC-SA 4.0. This page quotes it word for word and adds the headings, the order and the practice questions; references to the book's figures and stray spaces left by its formatting are removed. The page is shared under the same licence. Nothing here is sold.