What are hormones? Hormones also called chemical messengers or information molecules, are organic compounds secreted by endogenously located endocrine glands. They are generally released in the bloodstream (except gastrin) and have a specific effect on specific organs called target organs. The target organs are generally distantly located glands. A specific type of hormone is received by the specific target organs because of the presence of a specific receptor protein only in the target cell. The first hormone was discovered by English physiologists Starling and Bayliss, in 1903 from the duodenum of a patient. The hormone was secretin. The term hormone … Continue reading What are hormones? State the main points of differences between hormones and enzymes