insulin

How insulin controls blood glucose, why type 1 and type 2 diabetes differ, and how treatment moved from animal extracts to pumps, drugs, and stem cells.

How hormones work: chemical messengers, receptors, feedback loops, key hormones such as insulin and cortisol, and the endocrine disorders that follow.

The inventors of insulin assigned their patent for $1 so no one would be priced out of a lifesaving drug. A century later, US list prices ran roughly 11 times those of peer countries. Here is how that happened.