Pituitary Gland and Diabetes Insipidus

Diabetes Insipidus

When the Pituitary Gland is involved there are three types of diabetes insipidus: 

Central Diabetes Insipidus a deficiency of the hormone ADH (Anti-Diuretic Hormone) in the Posterior Pituitary Gland. The urine is very dilute but without the sugar taste of the urine associated with diabetes mellitus.

Neurogenic Diabetes Insipidus is an insensitivity of the kidneys to ADH that controls excretion of body fluid. The urine is very diluted sense the inability of the hormone ADH to restrict water loss. Again, like in Central Diabetes Insipidus, no glucose is present in the urine.

Iatrogenic Diabetes Insipidus - an artifact of medical drug use that causes the kidneys to excrete large amounts of urine. There is no glucose in the urine.

Diabetes Insipidus is characterized by excessive thirst and the excretion of large amounts of severely diluted urine, that, with a reduction of fluid intake, that has no effect on the concentration of the urine. This means the patient needs to continually take fluids into their body to prevent dehydration from the fluid loss excreted from the body. You need reserve water if you are exposed to conditions where excess water is lost normally.

Diabetes Mellitus and Diabetes Insipidus are two entirely separate conditions with unrelated mechanisms. Both cause the production of large amounts of urine (Polyuria). Diabetes Mellitus causes polyuria by a process called osmotic diuresis due to high blood sugar leaking into the urine and  carrying excess water with it. 

Osmosis is the process where water moves through a selectively permeable membrane from an area of low solute concentration to an area of high solute concentration. When leakage of blood glucose from the blood capillaries into the tubular ducts takes place it increases the solute concentration in the tube above that in the blood capillaries. Water, therefore, flows into the tubule by osmosis. Since this causes diuresis excretion from the kidneys along with the sugar the taste of urine in diabetes mellitus is sweet to the taste.