Thyroid
An under- or over-active gland — levothyroxine replacement and the antithyroid drugs.
Hypothyroidism: Replacing the Body's Thermostat
Thyroid hormone sets the speed of the entire body — when it runs low, everything slows down. The treatment is one of the simplest and most successful in all of medicine: a single daily tablet that exactly replaces the missing hormone. But the way we dose and monitor it is a perfect, real-world lesson in reading a feedback loop backwards.
Hyperthyroidism: Turning Down an Overactive Gland
If an underactive thyroid slows everything down, an overactive one speeds everything up — a racing heart, weight loss despite hunger, heat, tremor and anxiety. There are three quite different ways to bring it under control: block the gland with a drug, calm the symptoms while you wait, or destroy the overactive tissue for good. Knowing which does what — and the two rare but deadly emergencies to watch for — is the whole subject.
