Compare conditions

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

Hypothyroidism

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In one line

·The thyroid gland stops making enough hormone, so the whole body slows down—energy, warmth, digestion, heart rate, and mood all drop because every cell needs thyroid hormone to run at normal speed.

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Normal physiology

·The thyroid gland sits in the front of your neck, just below the Adam's apple, shaped like a small butterfly. Its only job is to make thyroid hormone (mostly T4, which cells convert to the active form T3), and this hormone travels through the blood to every cell in the body, telling each one how fast to work—how much fuel to burn, how much heat to make, how fast to build new proteins, and how quickly to do every task that keeps you alive.

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What goes wrong

·The thyroid gland either gets damaged so it can't make hormone anymore, or it's removed, or it doesn't have the raw materials it needs. Almost always, the root problem is in the thyroid itself—not the brain or pituitary.

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Hallmark signs

·Feeling tired all the time, even after sleeping
·Weight gain without eating more
·Feeling cold when others are comfortable
·Skin that feels dry and rough
·Hair that falls out or thins, especially on the head and outer third of the eyebrows
·Constipation (trouble having bowel movements)
·Feeling sad, down, or hopeless
·Thinking and remembering feel slower or fuzzy (brain fog)

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Red flags · escalate now

·Chest pain, trouble breathing, or a very slow heart rate (below 50 beats per minute)—these can signal myxedema coma, a life-threatening emergency where the body shuts down from severe thyroid deficiency.
·Severe confusion, extreme sleepiness, or passing out—signs that brain function is dropping dangerously low and you need emergency care right away.
·Body temperature below 95°F (35°C, measured with a thermometer)—the body can't make enough heat, and this can lead to organ failure without urgent treatment.
·Sudden, severe swelling in the neck that makes it hard to swallow or breathe—this can mean bleeding into a goiter (swollen thyroid) or rapid growth that presses on the windpipe and blocks air.

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Workup

·TSH (thyroid-stimulating hormone)
·Free T4 (free thyroxine)
·Anti-TPO antibodies (thyroid peroxidase antibodies)
·Lipid panel (total cholesterol, LDL, HDL, triglycerides)
·CBC (complete blood count)
·Creatine kinase (CK)

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Treatment

·Levothyroxine (synthetic T4 hormone) 1.6 mcg per kilogram of body weight per day, or start 25–50 mcg daily if older than 65 or if heart disease is present, then titrate every 6–8 weeks by checking TSH until TSH is 0.5–2.5 mIU/L
·Check TSH and free T4 at 6–8 weeks after starting or changing the levothyroxine dose, then adjust the dose by 12.5–25 mcg increments until TSH stays in the normal range (0.5–2.5 mIU/L)
·Take levothyroxine on an empty stomach 30–60 minutes before breakfast, and separate it from calcium supplements, iron, antacids, and soy by at least 4 hours
·In pregnancy, increase the levothyroxine dose by 25–30 percent as soon as pregnancy is confirmed, and check TSH every 4 weeks, aiming for TSH < 2.5 mIU/L in the first trimester and < 3.0 mIU/L in the second and third trimesters
·In older adults (over 65) or anyone with coronary artery disease or heart failure, start levothyroxine at 25 mcg daily and increase slowly (by 12.5–25 mcg every 4–6 weeks); accept a slightly higher TSH goal (up to 5–10 mIU/L) if symptoms improve and the heart stays stable
·If myxedema coma is suspected (confusion, body temperature under 95°F, slow breathing, low blood pressure), give IV levothyroxine 200–400 mcg once, then 50–100 mcg daily, plus IV hydrocortisone 100 mg every 8 hours, in the ICU

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NCLEX trap

·Start low in older adults or anyone with heart disease. Too much thyroid hormone too quickly can trigger a heart attack or dangerous heart rhythms. The safe move is to start at 25–50 mcg daily, wait 6–8 weeks, recheck TSH, then raise the dose step by step. Slow wins the race here.
·Fatigue and sadness are direct effects of low thyroid hormone slowing down the brain and body, not depression. Fix the thyroid first with levothyroxine and wait until TSH normalizes. If sadness stays after thyroid hormone is stable, then assess for depression.
·Younger patients usually feel best with TSH on the lower end of normal (around 1–2.5 mIU/L). Older patients and those with heart disease tolerate TSH a bit higher (2.5–4 mIU/L). Match the goal to the patient's age, heart health, and how they feel.
·Levothyroxine must be taken on an empty stomach, ideally 30–60 minutes before breakfast. Calcium, iron, antacids, and soy all block absorption. Take the pill alone in the morning, then wait to eat or take other pills.
·Hypothyroidism from Hashimoto disease (the most common cause) is lifelong. The immune attack on the thyroid never reverses. The patient will need levothyroxine forever and TSH checks every 6–12 months to keep the dose right as the body changes over time.
·A big thyroid in hypothyroidism means the immune system is attacking it (Hashimoto thyroiditis). TSH is high, T4 is low. The gland swells because TSH is beating on it, trying to squeeze out more hormone, but the gland is damaged and failing. This is hypothyroidism, not hyperthyroidism.

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