Insulin is a peptide hormone produced in the islets of Langerhans of the pancreas whose purpose is to regulate fat and carbohydrate metabolism in the human body. Insulin accomplishes this purpose by making the cells in muscle tissue and in the liver grab glucose from the bloodstream and store it as glycogen, which can then be used as an energy source for the cells. If insulin is not present, this transformation of glucose into glycogen does not occur, and the body has to use fat tissue as an energy source.
The level of insulin in the body is also used as a signal for other processes in the body. For example, the presence of insulin in the human brain seems to enhance memory and learning ability. The body's response to food intake also seems to be affected by the presence or absence of insulin.
When the human body fails to control properly its level of insulin, the result will be high blood sugar and diabetes mellitus, a metabolic disease with symptoms of thirst, hunger, and frequent urination. Type 1 diabetes is a result of the body failing to produce insulin; Type 2 diabetes is a result of the body developing insulin resistance. Gestational diabetes may also occur in a pregnant woman who has never had diabetes and who does have high blood sugar levels, but who generally does not have the other symptoms of diabetes. All types of diabetes require lifestyle changes with respect to diet and exercise.
Subcutaneous injections of insulin are used to treat those with Type 1 diabetes, and those with serious cases of gestational diabetes. These injections can be done via a single-use syringe with a needle, a repeated-use insulin pen, or an insulin pump. Those with Type 2 diabetes are treated with other types of medication because their bodies are resistant to the effects of insulin.
Biosynthetic insulin, manufactured via recombinant DNA technology, is the source of most insulin treatments. The most recent advances in recombinant DNA have created plants that produce human insulin more cheaply than previously had been possible. Some of these "insulin analogues" are designed not only to copy the exact effect of human-produced insulin, but also to have improved characteristics in other areas. For example, it can take several hours for human insulin to take effect after injection -- an "insulin analogue" has been developed that takes effect fifteen minutes after injection.
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