Insulin is an example of a protein hormone. This hormone contains 51 different amino acids, which are the building blocks of protein. People with diabetes either do not make enough insulin or are unable to use insulin efficiently.
Insulin is made up of two polypeptide chains tethered by disulfide bridges. One of the polypeptide chains has 21 amino acids, and the other chain has 30 amino acids. Insulin is one of the most important proteins in the human body, because it helps control the amount of glucose in the blood, according to the RCSB Protein Data Bank. Growth hormone, prolactin and oxytocin are just a few of the other protein hormones found in the human body.