RN Nursing · Medications Affecting the Endocrine System
Thyroid Medications: Hypothyroidism and Hyperthyroidism
A focused NCLEX-style review of thyroid pharmacology, covering levothyroxine for hypothyroidism, antithyroid agents (methimazole, PTU, iodine) for hyperthyroidism, and emergency management of thyroid storm.
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This note reviews the high-yield thyroid medications nursing students must master for exams: hormone replacement in hypothyroidism, antithyroid drugs in hyperthyroidism, and the emergency management of thyroid storm. Focus is on drug identification, mechanism, key nursing assessments, and common NCLEX traps.
Drug Identification
| Condition | Drug | Key Exam Clue |
|---|---|---|
| Hypothyroidism | Levothyroxine | T4 replacement |
| Hypothyroidism | Liothyronine | T3 (rarely used) |
| Hyperthyroidism | Methimazole | First-line antithyroid |
| Hyperthyroidism | Propylthiouracil (PTU) | Thyroid storm & pregnancy (1st trimester) |
| Hyperthyroidism | Potassium iodide | Short-term, pre-surgery |
Mechanism of Action
- Levothyroxine replaces deficient thyroid hormone (T4).
- Methimazole and PTU reduce thyroid hormone production.
- PTU also blocks peripheral conversion of T4 to T3.
- Iodine decreases thyroid hormone release in the short term.
Hypothyroidism vs. Hyperthyroidism
| Feature | Hypothyroidism | Hyperthyroidism |
|---|---|---|
| Heart rate | Bradycardia | Tachycardia |
| Temperature | Cold intolerance | Heat intolerance |
| Weight | Weight gain | Weight loss |
| Energy | Fatigue | Restlessness |
| Skin | Dry | Warm, moist |
Exam rule: Hypo = "Slow," Hyper = "Fast."
Levothyroxine (Most Tested)
- Take in the morning on an empty stomach.
- Do not switch brands.
- Lifelong therapy — takes weeks for full effect.
- Signs of overdose: tachycardia, chest pain, insomnia.
- Major risk: cardiac stress in elderly patients.
Antithyroid Medications (Methimazole & PTU)
- Used for Graves' disease.
- Used before thyroid surgery.
- PTU preferred in thyroid storm and in the first trimester of pregnancy.
Serious Risk: Agranulocytosis
- Report immediately any fever or sore throat.
- Monitor CBC and liver function (especially with PTU).
Thyroid Storm (Emergency)
- Life-threatening hyperthyroidism.
- Signs: high fever, severe tachycardia, hypertension, agitation.
- Treatment: PTU, beta-blockers, iodine, steroids.
- Exam priority: Stabilize airway and cardiac status first.
Nursing Safety Rules
- Check heart rate before giving levothyroxine.
- Do not give antithyroid drugs if WBC is critically low.
- Monitor for signs of infection.
- Avoid abrupt discontinuation of antithyroid drugs.
- Educate patients that symptom improvement takes weeks.
Common NCLEX Traps
- Giving levothyroxine at bedtime with food.
- Missing sore throat as a sign of agranulocytosis.
- Confusing hypo vs. hyper symptoms.
- Expecting immediate effect from levothyroxine.
- Forgetting cardiac monitoring in elderly patients.
Key Takeaways
- Levothyroxine replaces thyroid hormone for hypothyroidism — morning, empty stomach, lifelong, weeks to work.
- Methimazole and PTU reduce thyroid hormone production; PTU is preferred in thyroid storm and 1st-trimester pregnancy.
- Agranulocytosis is a life-threatening side effect of antithyroid drugs — report fever or sore throat immediately.
- Thyroid storm is a medical emergency: PTU, beta-blockers, iodine, steroids; stabilize airway and cardiac status first.
- Hypothyroidism = slow symptoms; hyperthyroidism = fast symptoms.
- Always check heart rate before giving levothyroxine, especially in elderly patients.
Test yourself on Thyroid Medications
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