Fat gain may also be linked to insulin resistance. Insulin resistance can cause glucose intolerance, which has been associated with fat gain, increased triglycerides, and the development of diabetes. Insulin is a hormone produced by the pancreas to control blood sugar-glucose. HIV medications may block or slow down the process by which insulin converts glucose to energy. In laboratory studies, Crixivan and higher doses of Norvir and Zerit have been shown to impair the action of insulin in fat and muscle cells. In this scenario the pancreas will tend to produce more and more insulin to compensate for the decrease in function. High insulin levels may be present for years before type 2 diabetes develops. A glucose tolerance test (GTT) may reveal that problem easily but it is hardly used in clinical practices. Additionally, some people may have a genetic predisposition to insulin resistance. A sedentary lifestyle and a diet rich in sugars and animal fats may also compound this problem. In any case, insulin resistance may just be a part of the mystery of lipohypertrophy. There is no agreement among researchers whether or not monitoring insulin levels in HIV-positive people is justifiable or dependable as a tool to assess insulin resistance and fat gain.