Hypothyroidism, Hyperthyroidism and Thyroid Storm

Medical-Surgical · Endocrine (Diabetes, Thyroid)·Updated 2026-10-28

What it is

Thyroid hormones (T3 and T4) set the body's metabolic rate, so hypothyroidism slows every system and hyperthyroidism speeds every system. In the United States, Hashimoto thyroiditis is the most common cause of hypothyroidism and Graves disease the most common cause of hyperthyroidism. The extremes are emergencies: thyroid storm is a life-threatening hypermetabolic crisis triggered by infection, surgery or stress in untreated hyperthyroidism, and myxedema coma is a hypometabolic crisis with hypothermia, hypoventilation and decreased consciousness.

What the NCLEX focuses on

Hyperthyroidism: tachycardia, palpitations, atrial fibrillation, fine tremor, heat intolerance, weight loss with increased appetite, diarrhea and, in Graves disease, exophthalmos; TSH low, free T4 high.
Hypothyroidism: fatigue, cold intolerance, weight gain, constipation, dry skin, bradycardia, heavy menses and slowed reflex relaxation; TSH high and free T4 low in primary disease.
Thyroid storm: high fever, severe tachycardia, agitation or delirium, vomiting and diarrhea, and heart failure.
Thyroid storm treatment: an antithyroid drug (PTU or methimazole), iodine at least 1 hour later, a beta blocker, an IV corticosteroid, cooling, and acetaminophen instead of aspirin.
Myxedema coma: hypothermia, bradycardia, hypoventilation, hypotension, hyponatremia and hypoglycemia; support ventilation, give IV levothyroxine and hydrocortisone, and rewarm passively.
Antithyroid drugs cause agranulocytosis (report sore throat, fever, mouth sores); PTU also causes liver injury and is preferred in the first trimester of pregnancy.
Hypothyroid clients metabolize drugs slowly, so opioids and sedatives cause respiratory depression; levothyroxine starts at a low dose in older adults and clients with heart disease.

Priority nursing actions

In thyroid storm, maintain the airway, give oxygen and start continuous cardiac monitoring.
Give the prescribed antithyroid drug, then iodine at least 1 hour later, a beta blocker and an IV corticosteroid.
Lower the temperature with acetaminophen and a cooling blanket.
Give prescribed IV fluids and monitor for heart failure, dysrhythmias and changing mental status.
Keep the room cool, quiet and calm, and identify the trigger.

Numbers to know

Value	Normal or target	Why it matters
TSH	0.4 to 4.2 microunits/mL (0.4 to 4.2 mU/L)	High in primary hypothyroidism; low in hyperthyroidism
Free T4	0.8 to 2.7 ng/dL (10 to 35 pmol/L)	Low in hypothyroidism; high in hyperthyroidism
Levothyroxine timing	30 to 60 minutes before breakfast on an empty stomach	Food reduces absorption
Separation from calcium, iron and antacids	At least 4 hours	These products bind levothyroxine
Iodine in thyroid storm	At least 1 hour after the antithyroid drug	Iodine given first fuels new hormone synthesis

Common exam traps

Choosing a heating pad or warm-water immersion for myxedema coma: wrong because active rewarming causes vasodilation and cardiovascular collapse; use warm blankets.
Choosing aspirin for fever in thyroid storm: wrong because aspirin displaces thyroid hormone from binding proteins and raises free hormone levels.
Choosing to give iodine before the antithyroid drug: wrong because iodine given first provides material for more thyroid hormone.
Choosing to treat sore throat and fever on methimazole as a cold: wrong because these signal agranulocytosis; hold the drug and obtain a WBC count.
Choosing to stop levothyroxine once laboratory results are normal: wrong because replacement is lifelong.

What to teach

Levothyroxine: take it every morning at the same time on an empty stomach, never stop it, and report palpitations, chest pain, insomnia or heat intolerance.
Antithyroid drugs: report sore throat, fever or mouth sores at once; with PTU, also report yellow skin or dark urine.
Exophthalmos: use prescribed lubricating eye drops, wear dark glasses and elevate the head of the bed at night.
Radioactive iodine: for the prescribed number of days, sleep apart and limit close contact, especially with children and pregnant women.

Client handout: Hypothyroidism and Levothyroxine (nurse guide and printable patient handout).

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Question 1 · QID 4A3530C6

The nurse receives handoff on four clients. Which client should the nurse assess first?

A. A client awaiting discharge teaching after parathyroidectomy with calcium 8.9 mg/dL, stable vital signs, and no neuromuscular symptoms
B. A client with hypothyroidism reporting three days of constipation despite prescribed stool softener use but no abdominal pain or vomiting
C. A client with type 2 diabetes whose fasting glucose is 155 mg/dL before breakfast and who reports no ketones or acute symptoms
D. A client with Graves disease whose temperature is 39.8°C with new confusion

Question 2 · QID 31F21E63

The nurse reinforces teaching for a client stabilized on levothyroxine. Which client statements indicate correct understanding? Select all that apply.

A. "I will take my calcium supplement at least four hours apart from this medication."
B. "I can stop the medication once my laboratory results are normal."
C. "I will report a racing heart, chest pain, or new trouble sleeping."
D. "I will take it at the same time every morning before eating."
E. "If I miss several days, I will take all the missed tablets together."

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Sources

Harding MM, Kwong J, Hagler D, Reinisch C. Lewis's Medical-Surgical Nursing: Assessment and Management of Clinical Problems. 12th ed. Elsevier; 2023; Chapter: Endocrine Problems.
Ross DS, Burch HB, Cooper DS, et al. 2016 American Thyroid Association Guidelines for Diagnosis and Management of Hyperthyroidism and Other Causes of Thyrotoxicosis. Thyroid. 2016;26(10):1343-1421.
Jonklaas J, Bianco AC, Bauer AJ, et al. Guidelines for the Treatment of Hypothyroidism. Thyroid. 2014;24(12):1670-1751.

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