Diabetes mellitus is a chronic metabolic disorder that prevents the body to utilize glucose completely or partially. It is characterized by raising glucose concentration in the blood and alterations in carbohydrate, protein and fat metabolism. This can be due to failure in the formation of insulin or liberation or action. Since insulin is produced by the ² cells of the islets of Langerhans, any receding in the number of functioning cells will decrease the amount of insulin that can be synthesized.

Many diabetics can produce sufficient insulin but some stimulus to the islets tissue is needed in order that secretion can take place. In the early stages of the disease the Insulin Like Activity (ILA) of the blood is often increased, but most of this insulin appears to be bound to protein and is not available for transport across the cell membrane and action of the cell.

The hormones of the anterior pituitary, adrenal cortex, thyroid and ± cells of the islets of Langerhans are glucogenic, that is, they increase the supply of glucose. Possibly they could increase the demand, decrease the secretion or antagonize and inhibit the action of insulin. The body releases hormones that raise blood glucose levels to provide a quick source of energy for coping with stress. In the stress conditions diabetes mellitus may precipitate with genetic predisposition.

Diabetes Insipidus is a condition that shares some of the symptoms of diabetes mellitus, large urine output, great thirst and sometimes a large appetite. But in diabetes insipidus these are symptoms of a specific injury, not a collection of metabolic disorders. The impaired pituitary gland produces less anti-diuretic hormone, a substance that normally helps the kidneys retain water.