Before GLP-1 drugs, before monoclonal antibodies, there was insulin — the first hormone deficiency ever treated with the hormone itself, the first drug purified from animal organs at industrial scale, and in 1982 the first genetically engineered drug ever approved. The molecule's two-chain structure, the 1921 discovery, the shift to recombinant production, and the amino-acid-substitution engineering behind rapid- and long-acting analogs.
Insulin
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Insulin: The Original Blockbuster Peptide -
Glucose and Insulin: The Body's Control Loop Blood glucose regulation is a textbook negative-feedback control system: a narrow setpoint, two antagonistic actuators, a sensor with a measurable lag, and a failure mode that modern medicine now patches with an actual external controller. A tour of the insulin-glucagon loop, what HbA1c and continuous glucose monitors really measure, how insulin resistance degrades the actuator, and how PID and model predictive control ended up running inside an insulin pump.