Compare conditions

Put any two — or three — conditions side by side, adult or pediatric, to spot the look-alike differences fast, row by row.

Hyperthyroidism

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In one line

·Thyroid hormone is your body's speed dial — it sets how fast your heart beats, how much heat you make, and how quickly you burn food for energy.

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Normal physiology

·The hypothalamus (a control center deep in your brain) tells the pituitary gland (a pea-sized gland just below it) to release TSH (thyroid-stimulating hormone) into your bloodstream. TSH travels to your thyroid gland (a butterfly-shaped gland in the front of your neck, just below your voice box). The thyroid makes two hormones: T4 (thyroxine, the storage form) and a little bit of T3 (triiodothyronine, the active form). T4 travels through your blood to your liver, kidneys, and other tissues, where an enzyme snips off one iodine atom and turns T4 into T3. T3 plugs into thyroid hormone receptors inside almost every cell in your body. Once plugged in, T3 tells the cell's DNA to make more energy-burning proteins, so your heart beats faster, your gut moves food along quicker, your brain fires faster, and your muscles burn more fuel. When enough T3 builds up, it sends a 'slow down' signal back to the hypothalamus and pituitary (negative feedback), so they make less TSH and the thyroid makes less hormone. That loop keeps your metabolism steady.

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What goes wrong

·Hyperthyroidism happens when your thyroid makes and releases way too much hormone, or when stored hormone leaks out all at once. The thyroid ignores the normal off switch, so T3 and T4 flood your bloodstream and tell every cell in your body to speed up. There are three main upstream breaks that cause this.

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Hallmark signs

·Fast heart rate (often over 100 beats per minute, even at rest)
·Fine shaking of the hands (tremor)
·Warm, sweaty skin
·Weight loss despite eating normally or more
·Feeling nervous, worried, or jittery
·Missed or irregular periods in women
·Bulging eyes (proptosis) and eyelid retraction (eyes look wide or staring)
·Enlarged, smooth thyroid gland (goiter) that you can feel in the neck

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Red flags · escalate now

·Fever over 104°F with confusion or agitation (possible thyroid storm)
·Heart rate above 140 at rest, chest pain, or trouble breathing (heart strain or failure)
·Sudden severe vision loss or eye pain (rare but urgent eye complication in Graves disease)
·New weakness in arms or legs, especially with low potassium on labs (thyrotoxic periodic paralysis)

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Workup

·TSH (thyroid-stimulating hormone)
·Free T4 (thyroxine)
·Free T3 (triiodothyronine)
·Thyroid-stimulating immunoglobulin (TSI) or TSH receptor antibody
·Radioactive iodine uptake scan (RAIU)
·Thyroid ultrasound
·EKG (electrocardiogram)

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Treatment

·Beta-blocker (propranolol 10–40 mg every 6–8 hours, or atenolol 25–100 mg daily)
·Methimazole (10–40 mg daily; or propylthiouracil 100–150 mg three times daily in first trimester pregnancy or thyroid storm)
·Radioactive iodine (I-131, single oral dose)
·Thyroid surgery (partial or total thyroidectomy)
·Corticosteroid (prednisone 40 mg daily, tapered over weeks) for subacute or silent thyroiditis
·Iodine solution (saturated potassium iodide or Lugol solution) in thyroid storm

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NCLEX trap

·A beta-blocker is a bridge — it makes the patient safe and comfortable by blocking the effects of too much thyroid hormone on the heart, but it does NOT stop the thyroid from making more hormone. You must also start an antithyroid medicine (methimazole or PTU) to actually block the thyroid from making more T4 and T3. Covering up the symptom is not the same as fixing the root problem.
·Each type has a different upstream break. In Graves disease, the immune system makes antibodies (TSI) that turn the thyroid ON, so you need antithyroid drugs to block new hormone-making. In a toxic nodule or toxic adenoma, a lump in the thyroid makes hormone on its own, ignoring the body's signals — these often need radioactive iodine or surgery. In thyroiditis (inflammation), the thyroid is leaking stored hormone into the blood, so it will stop on its own in a few weeks; you give anti-inflammatory medicine (NSAIDs or steroids), NOT antithyroid drugs. Match the treatment to the cause, not just to the fast heart rate.
·Too much thyroid hormone makes the heart pump harder and faster every single minute. Over weeks and months, this can wear out the heart's electrical system and trigger atrial fibrillation (an irregular, quivering heartbeat) (a chaotic, irregular heartbeat). Atrial fibrillation can let blood clots form in the heart, which can break off and cause a stroke. In severe cases — especially with infection, surgery, or trauma — the body can tip into thyroid storm, a life-threatening crisis with fever over 104°F, heart rates over 140, confusion, and shock. Move fast. Check an EKG. Treat it as urgent.
·Use PTU (propylthiouracil) in the first trimester of pregnancy to protect the baby. Methimazole can cross the placenta and cause rare but serious birth defects like scalp problems (aplasia cutis) and belly-button defects (omphalocele) in the first 12 weeks. After the first trimester, you can switch to methimazole because the risk is much lower and PTU carries a small risk of liver damage. Always ask if a woman of childbearing age is pregnant or planning to be before you pick the drug.
·In Graves disease, the immune system attacks TWO targets: the thyroid AND the fat and muscle tissue behind the eyes. Lowering thyroid hormone helps the heart and stops the hypermetabolism, but it does NOT stop the immune attack on the eyes. Eye problems (proptosis, double vision, dry eyes, redness) may stay the same or even get worse for months after thyroid hormone is controlled. Some patients need extra steroids, orbital radiation, or surgery to protect vision. Treat the thyroid, but watch the eyes separately — the two processes run on different timelines.
·Anxiety and hyperthyroidism can look almost identical: fast heart, sweating, nervousness, trembling hands. But in hyperthyroidism, the thyroid is flooding the blood with hormone, so TSH is very low (the pituitary shuts off because it sees too much thyroid hormone) and free T4 is high. In anxiety, TSH and free T4 are normal. Always measure thyroid hormone before you treat. The lab test is your proof — it tells you whether the problem is a broken thyroid or a worried mind.

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