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How does insulin resistance cause type 2 diabetes mellitus?

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An anatomical illustration of the human pancreas shows its location near the stomach and intestines, a detailed cross-section highlighting ducts and the islet of Langerhans, and an inset of pancreatic tissue histology with labeled alpha, beta, and delta cells. — diabetes mellitus The islets of Langerhans are responsible for the endocrine function of the pancreas. Each islet contains beta, alpha, delta, and pancreatic polypeptide (PP) cells that are responsible for the secretion of pancreatic hormones. Beta cells secrete insulin, a well-characterized hormone that plays an important role in regulating glucose metabolism.

In the context of diabetes mellitus, insulin resistance is a primary factor in the development of type 2 diabetes.1

Insulin is a hormone responsible for signaling cells—particularly muscle and adipose cells—to take up and metabolize glucose from the bloodstream for energy. Insulin resistance occurs when these cells exhibit a reduced sensitivity to the effects of insulin, meaning they are less able to effectively absorb glucose.2341

Because the cells do not respond properly to insulin, they take up less glucose from the blood, which causes blood glucose levels to rise, a condition known as hyperglycemia. Over time, this inability to regulate blood sugar effectively characterizes the progression of type 2 diabetes. While insulin resistance is a key mechanism, type 2 diabetes is often associated with a combination of this resistance and varying degrees of insulin deficiency.214