Did you know that there are actually three general types of diabetes? Diabetes comes from a Greek word that simply means excessive urine. It was recognized as a specific disease millennia ago by Egyptian and Greek physicians. All three forms of diabetes involve problems with hormones: the two most common forms involve the hormone insulin and the third involves a hormone called ADH or vasopressin.
Diabetes mellitus (“sweet urine”) results from excessive sugar in the blood, specifically glucose, which passes into the kidney tubules and is insufficiently reabsorbed into the blood. This high urine glucose concentration draws extra water along with it into the bladder, causing it to fill more rapidly. The two types of diabetes mellitus are Type I (or juvenile-onset) diabetes, and Type II (or maturity-onset) diabetes.
Type I diabetes is caused by loss or destruction of insulin-secreting cells (beta cells) of the endocrine pancreas. The reasons for loss of these cells are not clear, but it usually occurs in childhood. This condition may result from viral infection followed by an auto-immune reaction. There may be a genetic component to the susceptibility to this type of diabetes. Type I diabetes is less common than Type II diabetes. Insulin is the key hormone that promotes uptake of sugar into muscle and fat, and many other tissues, although the brain can use glucose without insulin. If insulin is not produced by the endocrine pancreas (islet cells), then blood glucose is not taken up into most tissues, and blood sugar levels rise.
Type II diabetes is usually a result of decreased insulin receptors on cell surface membranes. A receptor is a molecule that binds to a hormone (or to some other communication molecule) and that brokers its effects on a target. Type II diabetes normally occurs in older, overweight individuals, but with the onset of the obesity epidemic in America, even younger children are suffering from this form of diabetes. Again, causes of the disease are not entirely clear, but there is definitely a genetic component involved, which is made worse by obesity and stress.
Diabetes insipidus is a third type of diabetes, which is much rarer than diabetes mellitus and does not involve sugar in the urine. Diabetes insipidus is caused by a decrease or loss in the production of a pituitary hormone known as anti-diuretic hormone (ADH) or vasopressin. This small molecule is secreted by the posterior pituitary gland. It is a major hormone involved in the regulation of body fluid volume and blood pressure. Vasopressin acts on kidney tubules to promote water reuptake into the blood from the urine.
This type of diabetes is rare, but it can occur following a blow to the head, or with blood loss to the lower part of the brain, or damageof the pituatary stalk with a brain tumor. The secretion of ADH/vasopressin is inhibited by alcohol, and thus alcohol consumption also increases urine output, but its effects are reversible.