Thyroid hormone sets the speed of every cell. Too little and the whole body slows; too much and it races. There are only two moves — replace the hormone or block it — and giving the wrong one makes the patient worse. Pick a patient, pick a drug, watch what happens.
Euthyroid
TSH—0.4–4.0 mIU/L
Free T4—0.8–1.8 ng/dL
Apical HR—60–100 bpm
Tap the gland, heart, gut, or face — or use the list →