What are the genetic changes related to type A insulin resistance syndrome ?
Type A insulin resistance syndrome results from mutations in the INSR gene. This gene provides instructions for making a protein called an insulin receptor, which is found in many types of cells. Insulin receptors are embedded in the outer membrane surrounding the cell, where they attach (bind) to insulin circulating in the bloodstream. This binding triggers signaling pathways that influence many cell functions.  Most of the INSR gene mutations that cause type A insulin resistance syndrome lead to the production of a faulty insulin receptor that cannot transmit signals properly. Although insulin is present in the bloodstream, the defective receptors make it less able to exert its effects on cells and tissues. This severe resistance to the effects of insulin impairs blood sugar regulation and leads to diabetes mellitus. In females with type A insulin resistance syndrome, excess insulin in the bloodstream interacts with hormonal factors during adolescence to cause abnormalities of the menstrual cycle, ovarian cysts, and other features of the disorder.  This condition is designated as type A to distinguish it from type B insulin resistance syndrome. Although the two disorders have similar signs and symptoms, type B is not caused by INSR gene mutations; instead, it results from an abnormality of the immune system that blocks insulin receptor function.