The amount of glucose in the blood is controlled primarily by the two hormones, insulin and glucagon. Too much or too little of these two hormones can cause the blood sugar levels to drop too low (hypoglycemia) or rise too high (hyperglycemia). Cortisol, growth hormone, and catecholamines (epinephrine and norepinephrine) can also influence the blood sugar levels. The pancreas, a gland in the upper abdomen, produces both insulin and glucagon. The pancreas contains a hormone-producing tissue called the islets of Langerhans.

When blood sugar levels rise after a meal, the beta cells in the islets of Langerhans release insulin. The insulin helps glucose enter the body cells, lowering the blood levels of glucose to the normal range. When blood sugar falls too low, the alpha cells, also located in the islets of Langerhans, secrete glucagon. This triggers the liver to release stored glycogen and change it into glucose, thus raising blood sugar levels to the normal range. The body’s muscles also store glycogen and can be called upon to convert that glycogen into glucose.