Thyroid hormone is the body’s metabolic accelerator. Too much of it and everything
runs hot and fast: heart rate up, temperature up, bowels up, weight down. Learn this page as the
mirror image of NG-285 (Hypothyroidism) — same sections, same diagrams, opposite findings — and the
two stop blurring together. The one number that catches students out: in primary disease
TSH goes the OPPOSITE way to T3/T4, so hyperthyroidism has a LOW TSH.
🔥 HIGH & HOTFast heart · hot skin · weight loss · diarrhea · anxious & shaky.
🧪 TSH ↓ · T3/T4 ↑Primary disease: TSH is the opposite of the hormones.
👁️ Graves’ extrasExophthalmos + goitre + pretibial myxedema — antibody disease, not just “too much hormone”.
A butterfly-shaped gland sitting on the windpipe that sets the speed of every cell in the body.
🦋 Anatomy first — normal gland vs goitre
Two lobes joined by an isthmus, wrapped round the trachea just below the
cricoid cartilage. It is the most superficial endocrine gland in the body — which is why you can
see and feel disease here that you would never detect in an adrenal or a pituitary.
🧠 Butterfly on the windpipe. Two wings (lobes) + a body (isthmus) resting on the trachea.
⚙️ What T3 and T4 actually do
They set the basal metabolic rate — how fast every cell burns fuel.
Heat production (body temperature)
Heart rate, contractility and cardiac output
Gut motility
Growth and brain development in children
How fast other drugs and hormones are used up
T4 is the storage form the gland mostly releases; T3 is the active form tissues convert it into.
🧠 T3 = the “Three-times stronger” one. T4 is the tank, T3 is the flame.
🧬 Iodine is the raw material
The gland traps dietary iodine and bolts it onto tyrosine to build hormone.
T4 carries four iodines, T3 carries three.
That is why too much iodine — contrast dye, amiodarone, kelp/seaweed supplements —
can tip a susceptible gland into overproduction.
🧠 Count the iodines: T4 = 4 iodine, T3 = 3 iodine.
⭐ Cause #1 — Graves’ disease
Autoimmune. The body makes an antibody (thyroid-stimulating immunoglobulin) that
imitates TSH and jams the TSH receptor permanently ON.
Because it is an antibody disease and not just excess hormone, Graves’ brings extras that
other causes do not: exophthalmos, goitre, and thickened shiny skin over the shins
(pretibial myxedema).
Most common in women, typically 20–40 years old.
🧠 GRAVES = GAINS “HIGH”. The antibody grabs the receptor and never lets go.
Thyroiditis — an inflamed gland leaks stored hormone. Often transient, and it can be
followed by a hypothyroid phase.
Too much iodine — contrast, amiodarone, kelp.
Too much levothyroxine — over-replacement or misuse for weight loss. Iatrogenic and common.
Rarely, a TSH-secreting pituitary tumor (then TSH is HIGH — see the labs section).
🧠 Ask every hyperthyroid patient two questions: “What supplements do you take?” and
“Have you had a CT with contrast?”
🔬 Down at the microscope — the follicle
Thyroid tissue is a field of follicles: a ring of cells around a pool of
colloid, which is stored hormone. In overdrive the cells grow tall and eat the colloid away —
the gland is spending its savings.
🧠 Colloid = the pantry. Hyperthyroid empties it; Hashimoto’s destroys the kitchen.
🎈 Goitre — an enlarged gland, not a diagnosis
A goitre just means the gland is big. It happens in hyperthyroidism, in hypothyroidism, and in
iodine deficiency — so it never tells you the direction on its own.
Never palpate the neck vigorously in known or suspected hyperthyroidism — hard
palpation can squeeze stored hormone into the circulation and help trigger a thyroid storm.
🧠 “Golf balls in the throat.” Big gland → pressure → hoarseness, dysphagia, stridor.
🔥
HIGH & HOT — THE SIGNS
STEP 2 · CLUES
One rule generates every symptom: metabolism is running too fast. Predict, don’t memorize.
🧍 Head to toe — hyper on the left, hypo on the right
🧠 Cover one column with your hand and rebuild it from the other. If you can do that,
you own both pages.
❤️ Cardiac — the system that kills
Tachycardia >100 at rest (normal 60–100)
Palpitations and atrial fibrillation — the classic complication in older patients
Systolic hypertension with a widened pulse pressure (e.g. 160/60)
Muscle wasting, especially the proximal muscles (rising from a chair, combing hair)
Diet: high calorie, high protein, high carbohydrate, with snacks between meals.
Some sources cite 4,000–5,000 kcal/day in severe untreated disease.
Keep fiber low because the gut is already too fast, and avoid caffeine and other stimulants.
🧠 Eating like a teenager, shrinking like a marathon runner.
New agitation or confusion in a hyperthyroid patient is an early thyroid storm until proven otherwise.
🧠 Wired but tired. The engine is racing and the tank is empty.
👁️ Exophthalmos — a Graves’ problem, not a hormone problem
🧠 “Grape eyes.” Treating the labs does not put the eyes back — protect the cornea.
👩 Reproductive & skin
Amenorrhoea or light, infrequent periods (hypothyroid does the opposite — heavy periods)
Reduced fertility; in men, gynaecomastia and reduced libido
Fine, soft, thinning hair; smooth velvety skin; brittle nails
Rare but classic in Graves’: thickened, shiny, orange-peel skin over the shins
(pretibial myxedema)
🧠 Fast metabolism burns off periods. Hyper = less bleeding, hypo = more.
📊 Side by side — the mirror table
Body system
HYPERthyroid 🔥
HYPOthyroid 🧊
Heart rate
Tachycardia, A-fib, palpitations
Bradycardia, low voltage ECG
Blood pressure
Systolic HTN, wide pulse pressure
Diastolic HTN, narrow pulse pressure
Temperature
Heat intolerance, warm MOIST skin
Cold intolerance, cool DRY skin
Weight
LOSS with increased appetite
GAIN with reduced appetite
Bowels
Diarrhea
Constipation
Mood / cognition
Anxious, irritable, insomnia
Depressed, apathetic, forgetful
Reflexes
Brisk / hyperreflexia
Slow relaxation phase
Periods
Light or absent (amenorrhoea)
Heavy / irregular (menorrhagia)
Hair & skin
Fine thinning hair, smooth skin
Coarse hair, hair loss, dry scaly skin
Eyes
Exophthalmos, lid lag (Graves’)
Puffy periorbital edema, lost outer brow
Emergency
THYROID STORM
MYXEDEMA COMA
🧠 Every row is a see-saw. Learn the left, flip it, and you have the right.
🧪
READING THE LABS
STEP 3 · CONFIRM
This is the same logic on NG-285 — learn it once and it answers both pages.
🧪 The three patterns you must recognize
🧠 “TSH is always the opposite of T3 and T4” — in primary disease.
Read T3/T4 first, then check which way TSH went.
🔁 The loop — why TSH moves backwards
🧪 TSH is the screening test
TSH is the most sensitive single test of thyroid function, because the pituitary reacts to tiny
changes in circulating hormone long before the patient notices anything.
In primary hyperthyroidism, TSH is suppressed — low or undetectable.
Reference ranges vary between labs and shift in pregnancy and older age — always read the range printed
beside the result rather than memorizing a number.
🧠 TSH = the thermostat reading. Room too hot → thermostat turns the heating off.
🧪 Free T4 and T3 confirm it
Once TSH is abnormal, free T4 (and often T3) tells you the size and the direction of the problem.
TSH low + free T4 high = overt hyperthyroidism
TSH low + free T4 normal = subclinical hyperthyroidism (still raises A-fib and osteoporosis risk)
A small group are “T3 toxic” — T3 high with a normal T4
🧠 TSH says “something is wrong”; free T4 says “this is how wrong”.
Radioactive iodine uptake scan (RAIU) — a hot, diffusely active gland = Graves’; hot nodules
with a cold background = toxic nodular disease; a cold, low-uptake gland = thyroiditis or an
iodine load
Ultrasound for nodules and gland size
🧠 Antibodies answer “why”. RAIU answers “where”.
⚠️ The classic exam traps
Choosing “TSH high” for hyperthyroidism because both start with the same idea of “high”.
In primary disease it is LOW.
Forgetting secondary/central disease: if TSH and T3/T4 point the same way, the pituitary
is the problem, not the gland.
Other results you may see: low cholesterol, high blood glucose, high calcium,
and a low hematocrit.
🧠 Opposite arrows = gland. Same arrows = pituitary.
Both block hormone synthesis. They do not touch hormone already stored, so relief takes
weeks, not days.
Methimazole — usually first choice outside the first trimester of pregnancy
Propylthiouracil (PTU) — preferred in the first trimester; also blocks T4→T3 conversion,
which is why it appears in storm protocols. Carries a liver injury warning.
Report immediately: fever, sore throat, mouth ulcers — these can signal
agranulocytosis, a dangerous drop in white cells.
Also report yellowing of the eyes or skin, dark urine, and right upper quadrant pain (liver).
🧠 PTU “Puts the Thyroid Under” — and it is the Pregnancy (first trimester) choice.
💊 Beta-blockers — symptom rescue
Propranolol and other “-olol” drugs do nothing to the gland. They mask the sympathetic
symptoms while the antithyroid drug works.
Slows heart rate, softens tremor, calms anxiety
Hold and check if HR is below 60 or the blood pressure is low —
follow the parameters on the order
Use with caution in asthma and in decompensated heart failure
🧠 “-lol” = Lowers heart rate, Lowers BP. A bridge, not a cure.
💊 Iodine solutions (SSKI / Lugol’s)
Large doses of iodine temporarily shrink the gland and reduce its blood supply — used before
surgery and in a storm.
Dilute it in juice or water and give it through a straw — it stains teeth
Give it after the antithyroid drug, separated by about an hour
Take with food to reduce gastric upset
Report a brassy taste, burning mouth or sore gums
🧠 SSKI: Shrinks the gland · Stains the teeth · Keep it apart from other doses.
☢️ Radioactive iodine (RAI) — the common definitive treatment
An oral dose the gland absorbs, which destroys overactive tissue over weeks.
The patient is awake — this is not a surgical procedure.
Before: confirm a negative pregnancy test (it is absolutely contraindicated in pregnancy
and breastfeeding), stop antithyroid drugs for a few days as directed, remove neck jewelry and
dentures, and follow the fasting instructions given.
After — radiation precautions for several days per protocol:
Avoid close prolonged contact, especially with pregnant people, infants and children
Sleep alone; avoid crowds and public transport
Use a separate toilet if possible, sit to void, and flush 2–3 times
Do not share utensils, towels or laundry; wash them separately
Increase fluids to clear the isotope faster
Expect hypothyroidism afterwards — most patients end up on lifelong levothyroxine, which is a
planned outcome and not a complication.
🧠 RAI today = levothyroxine tomorrow. The cure for hyper is often a controlled hypo.
Positioning: semi-Fowler’s, 30–45°, with the head
and neck in neutral alignment. Support the head with both hands when turning.
Do not let the patient flex or hyperextend the neck, and do not lie them flat.
Also expect: humidified air, encouragement to cough and deep breathe while supporting the neck,
and a soft or liquid diet initially.
🧠 A · B · C · C — Airway, Bleeding, voice (Breathing), Calcium.
Artificial tears during the day; lubricating ointment at night
Dark glasses outdoors — light sensitivity and wind irritation
Elevate the head of the bed to drain periorbital fluid
Restrict sodium to reduce swelling
Tape the lids shut or wear an eye shield at night if they do not close
Do full eye range-of-motion exercises to keep the muscles supple
Stop smoking — it is the strongest modifiable risk factor for the eye disease
Never massage the eyeball.
🧠 Tears · Tint · Tilt · Tape.
🧠 Quiz yourself — no peeking
8 questions with answers
Q1: A patient with Graves’ disease has TSH 0.02 and free T4 high.
Which gland has the problem?
The thyroid. The arrows point in opposite directions, which is the signature of PRIMARY
disease. The pituitary is behaving correctly by shutting TSH off.
Q2: Which finding in a hyperthyroid patient would you report first — temperature
38.2 °C, HR 108, three loose stools, or new confusion?
New confusion. A change in level of consciousness is the earliest sign of thyroid storm and
outranks the other three, which are all expected findings in hyperthyroidism.
Q3: Why is aspirin contraindicated in thyroid storm?
Salicylates displace thyroid hormone from its binding protein, raising the free
(active) hormone level and making the crisis worse.
Q4: A post-thyroidectomy patient reports tingling around the mouth and fingertips.
What is happening and what do you do?
Hypocalcemia from parathyroid injury. Check calcium, assess for Chvostek’s and Trousseau’s
signs, notify the provider, and keep IV calcium gluconate and seizure precautions available.
Q5: Which post-op finding needs the fastest response — a hoarse voice, a dressing with a
small amount of dry drainage, noisy breathing, or a reported sore throat?
Noisy breathing / stridor. That is an airway obstruction — from swelling, hematoma or
laryngospasm — and it needs immediate action.
Q6: A patient on methimazole calls with a fever and a very sore throat. What do you tell them?
Stop guessing and be seen today — this can be agranulocytosis. They need an urgent white
cell count before the next dose.
Q7: What diet do you plan for an untreated hyperthyroid patient?
High calorie, high protein, high carbohydrate, with frequent snacks. Keep fiber low because
the gut is already too fast, and avoid caffeine and other stimulants.
Q8: A patient is going home after radioactive iodine. Name three precautions.
Any three of: avoid close contact with pregnant people and young children, sleep alone,
use a separate toilet and flush two to three times, do not share utensils or laundry, and increase
fluids — for the number of days specified by the protocol.