Insulin, types of insulin and reactions of insulin

Insulin 
Since the discovery of insulin, many advances ­been made in its commercial preparation from the pancreas of animals, primarily cattle and swine. Its production is carefully controlled to ensure the number of of insulin per volume when the product is purchaser: the diabetic patient. Insulin can be administered hypodermically because it is a protein; if taken orally, it would undergo enzymatic digestion in the gastroin­nal tract, which would absorb its constituent amino acids ­not the intact, active hormone.
Types of insulin 
There are several types of insulins available fi treatment of the insulin-dependent diabetic patient. They: differ primarily in the rate of onset and duration ofa which is reflected in the three classifications-rapi, termediate, and long-acting. The most ­commonly used insulins today are the two in term ­acting ones, Lente and NPH (Neutral Protarr:. Hagedorn). They are stable solutions of insulin tha sess the desirable properties of relatively rapid onset 2-8 hours) and moderately prolonged duration of a, (24-28 hr). Regular insulin is used in the treatmer;. ketoacidosis because its rapid onset of action permits physician to monitor blood glucose levels and adjust insulin injections to the need of the patient.
It must be recognized that the action of exog' insulin injected hypodermically, usually once a day, is not the same physiologically as tha t of endogenous ins­released by the beta cells of the pancreas in response to ingestion of food. Exogenous insulin is continuously avail­able in the bloodstream and, therefore, the patient must adjust to it by consuming properly spaced meals. Al­though the mechanism that causes this is not understood, it has been observed that exercise enhances glucose uti­liza tion in the diabetic. The research of Pederson and co­workers indicates that postprandial exercise was associ­ated with a significant rise in insulin binding receptor sites on the cells that they studied-erythrocytes and monocytes. Therefore, if an insulin-dependent diabetic patient increases his activity significantly on anyone day, he must increase his food intake or decrease his usual insulin dose for that day.
The stable IDDM patient usually requires one injec­tion before breakfast of intermediate acting insulin to achieve reasonable control of blood sugar. However, some labile insulin-dependent diabetics require two injections to achieve reasonable control during the day and to avoid nocturnal hyperglycemia. One injection is given in the morning before breakfast and the second one preceding the evening meal or a feeding at bedtime. The quantity of insulin injected varies with each patient. Presently a con­tinuous subcutaneous insulin infusion pump and an ar­tificial pancreas are being tested in the hope of controlling the daily excursions in blood glucose levels that occur with the usual injections of insulin once or twice a day.
Insulin reactions 
Hypoglycemic episodes in the diabetic due to excess insulin are to be avoided because prolonged and repea ted insulin reactions lead to irreversible damage to the corti­cal neurons. Most of these reactions occur because the patient has not properly spaced his food intake or has omitted a meal entirely. They can also occur because of an unplanned increase in activity or the injection of the wrong dose of insulin.
Intermediate- and long-acting insulins in excess pro­duce a gradual decrease in blood glucose levels. The pa­tient experiences headache, blurred or double vision, fine tremors, uncontrollable yawning, mental confusion, and incoordination. Ifthese symptoms are not treated, uncon­sciousness ensues. The insulin reaction in a patient who is conscious can be treated by an oral glucose solution, such as frui t juice and sweetened carbonated beverages or with sugar. Diabetic patients using intermediate- or long-act­ing insulin are advised to carry with them at all times a source of glucose, such as sugar cubes, candy, or a special tube of concentrated glucose.
Whenever the ability of the patient to swallow with­out aspiration is in question or he is unconscious, the hormone glucagon is injected subcu taneously to stimulate gluconeogenesis. When conscious, the patient is offered an oral glucose solution. If the patient is in a hospital, the glucagon injection may be followed by intravenous dex­trose in water.

Hypoglycemic hyperglycemia
Episodes of mild hypoglycemia followed almost im­mediately by hyperglycemia have been observed in patients using intermediate-acting insulin. Hypo­glycemia, a reaction occurring at the peak time of insulin action, activates a counter-regulatory hormonal response characterized by the release of epinephrine, adrenal corticosteroids, and growth hormone. This hormonal re­lease is a strong stimulus to gluconeogenesis, with the result that rebound hyperglycemia occurs. In other words, "hypoglycemia begets hyperglycemia." This swing in blood glucose is also knovvn as the Symogyi effect. The problem is caused by too much insulin and is treated by slowly reducing the daily dose of insulin.