Insulin

Insulin is a hormone secreted by the pancreas gland, one of the glands in the endocrine system. Insulin, working in harmony with other hormones, regulates the level of blood sugar (glucose). An insufficient level of insulin secretion leads to high blood sugar, a disease called diabetes mellitus.

Endocrine glands are ductless glands; that is, they pour their products (hormones) directly into the bloodstream. The pancreas, a gland in the upper abdomen, has cells within it that secrete insulin directly into the bloodstream.