In the 1850's, scientists first recognized that the thyroid gland produced a substance which regulated metabolism. A decade later, it was noted that the pancreas acted as a gland, secreting a substance that would later be identified as insulin. Hormones are chemical messengers. Adrenalin is a hormone. The male equivalent is testosterone.
Various hormones have various roles.
Prolactin is responsible for regulating milk production while insulin regulates blood sugar levels. There exists a separate group of hormones that regulate growth. Two decades after GH was discovered, an even more powerful growth factor was found. However, its function is nothing like insulin. I been discovered before GH, it would have received that name.