Graves disease vs Subacute thyroiditis
How to tell Graves disease and Subacute thyroiditis apart when a board question makes them look alike.
Graves actively makes new hormone with high uptake; thyroiditis leaks stored hormone with low uptake.
Side by side
Hyperthyroidism with diffuse goiter, eye findings, thyroid-stimulating antibodies, and high uptake.
Painful tender thyroid after viral illness with transient thyrotoxicosis and low uptake.
Autoantibodies stimulate the TSH receptor to make new thyroid hormone.
Inflammation releases preformed thyroid hormone from damaged follicles.
Low TSH, high free T4 and T3, positive TSI or TRAb antibodies, diffuse nontender enlarged thyroid with audible bruit, exophthalmos, pretibial myxedema, and elevated diffuse radioactive iodine uptake support Graves disease.
Low TSH, high free T4 and T3 transiently, tender enlarged thyroid often with referred jaw or ear pain after recent upper respiratory infection, markedly elevated ESR, and near-zero radioactive iodine uptake support subacute (de Quervain) thyroiditis; expect transient hyperthyroid phase, then hypothyroid phase, then recovery.
The trap
Both cause low TSH, elevated free T4 and T3, and thyrotoxic symptoms (palpitations, weight loss, heat intolerance), so labs alone do not pick the diagnosis. The deciding bedside features are the thyroid exam and the radioactive iodine uptake. Diffuse nontender thyroid enlargement with audible bruit plus exophthalmos plus pretibial myxedema is Graves; diffuse tender thyroid plus jaw or ear pain plus recent upper respiratory infection plus markedly elevated ESR is subacute thyroiditis. Radioactive iodine uptake closes it: high diffuse uptake equals Graves (treat with methimazole, RAI ablation, or thyroidectomy); near-zero uptake equals thyroiditis releasing preformed hormone (treat with NSAIDs or short-course prednisone if severe; the disease is self-limited and often passes through transient hyperthyroid then hypothyroid phases before recovery).
Watch it explained
The repair move
For thyrotoxicosis, three steps in order: (1) examine the thyroid (diffuse nontender with bruit suggests Graves; diffuse tender suggests subacute thyroiditis; nodular suggests toxic adenoma or toxic multinodular goiter); (2) check radioactive iodine uptake (high diffuse uptake equals Graves; high focal uptake equals toxic adenoma; near-zero uptake equals thyroiditis or exogenous thyroid hormone use); (3) target the cause (Graves with methimazole then RAI ablation or thyroidectomy; subacute thyroiditis with NSAIDs and beta-blocker for symptom control until self-limited resolution; expect a transient hypothyroid phase before recovery).
Try a free question
CoreA patient has weight loss, tremor, diffuse goiter, eye findings, suppressed TSH, elevated T4, and diffusely increased radioactive iodine uptake. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Graves disease. Thyroid-stimulating antibodies drive new hormone production and high uptake in Graves disease.
Why the other choices are tempting
- B. Subacute thyroiditis releases stored hormone and has low uptake.
- C. Toxic adenoma causes focal, not diffuse, uptake.
- D. Pheochromocytoma causes catecholamine spells with normal thyroid hormone.
- E. Hashimoto is usually hypothyroid after autoimmune destruction.
Flashcards
Tap a card to flip it.
What is the fastest separator for Graves disease vs Subacute thyroiditis?
Graves actively makes new hormone with high uptake; thyroiditis leaks stored hormone with low uptake.
What clue should make you choose Graves disease?
Hyperthyroidism with diffuse goiter, eye findings, thyroid-stimulating antibodies, and high uptake.
Quick answers
What is the fastest way to tell Graves disease from Subacute thyroiditis?
Graves actively makes new hormone with high uptake; thyroiditis leaks stored hormone with low uptake.
What is the key clue for Graves disease?
Hyperthyroidism with diffuse goiter, eye findings, thyroid-stimulating antibodies, and high uptake.
What is the key clue for Subacute thyroiditis?
Painful tender thyroid after viral illness with transient thyrotoxicosis and low uptake.
What is the common trap with Graves disease vs Subacute thyroiditis?
Both cause low TSH, elevated free T4 and T3, and thyrotoxic symptoms (palpitations, weight loss, heat intolerance), so labs alone do not pick the diagnosis. The deciding bedside features are the thyroid exam and the radioactive iodine uptake. Diffuse nontender thyroid enlargement with audible bruit plus exophthalmos plus pretibial myxedema is Graves; diffuse tender thyroid plus jaw or ear pain plus recent upper respiratory infection plus markedly elevated ESR is subacute thyroiditis. Radioactive iodine uptake closes it: high diffuse uptake equals Graves (treat with methimazole, RAI ablation, or thyroidectomy); near-zero uptake equals thyroiditis releasing preformed hormone (treat with NSAIDs or short-course prednisone if severe; the disease is self-limited and often passes through transient hyperthyroid then hypothyroid phases before recovery).