Physiologic effects of Insulin

Insulin is secreted by pancreatic beta cells (ß), located in the islets of Langerhans. The islets of Langerhans are clusters of four cell types, (alpha, beta, delta, and F) surrounded by pancreatic ancini. Drag your cursor over the map to identify cells and their related products.

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The pancreatic islet cell that is responsible for secreting insulin is the alpha cell.

Insulin has the following important effects on body tissues:
Anabolism – the metabolic process that constructs complex molecules from simple ones.
Glycogenolysis - the conversion of glycogen stored in the liver or muscle cells into glucose
Gluconeogenesis - the formation of glucose from non-carbohydrate sources such as amino acids during fasting and starvation.
Protein synthesis - protein formation from amino acids by stimulating the entry of amino acids into cells
Lipogenesis - the synthesis and storage of fat

The term "endogenous" insulin refers to insulin produced by beta cells in the pancreas. "Exogenous" insulin is a term used to describe pharmaceutical insulin. Counter-regulatory hormones are hormones that block the effects of insulin, thus increasing blood glucose. Important counter-regulatory hormones include: glucagon, epinephrine, norepinephrine, growth hormone, and cortisol. Blood glucose management in diabetes must account for the release of one or more of these counter-regulatory hormones throughout the day.

Insulin is essential for normal carbohydrate, protein and fat metabolism. People with type 1 diabetes (T1D) produce little to no endogenous insulin and therefore require exogenous insulin for survival. Although people with type 2 diabetes (T2D) produce endogenous insulin, over time many experience a progressive loss of beta cell function and may require supplemental exogenous insulin for adequate blood glucose control. Times of stress or illness can substantially increase the need for insulin. This is why the designation "T2D" has replaced the former term "non-insulin dependent diabetes mellitus."

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