How are insulin and other hormones obtained from animal sources?

Historically, insulin and other hormones were obtained from animal sources through extraction processes from specific organs. For insulin, the pancreas of pigs, cows, and sheep served as the primary source for approximately 50 years.12

The process of isolating insulin from these animal pancreases was complex because the organ contains digestive enzymes that can destroy the hormone. To successfully extract it, scientists developed methods such as tying off pancreatic ducts to cause the enzyme-secreting acinar cells to die, followed by homogenizing the remaining tissue and extracting it using ethyl alcohol and acid.1

Other hormones were also sourced from animals; for example, human growth hormone was previously obtained from the pituitary glands of cadavers because the hormone's effects are species-specific, making animal alternatives ineffective for humans.3

Today, these methods have largely been replaced by recombinant DNA technology. Pharmaceutical companies now synthesize hormones like insulin by incorporating specific DNA sequences into bacteria such as Escherichia coli, allowing for the production of human-identical proteins.13