Glucose clamp technique

Glucose clamp technique: a method for quantifying insulin secretion and resistance. by R. A. DeFronzo and others separates two questions. In a hyperglycemic clamp, variable glucose infusion holds blood glucose above baseline while sampled insulin reports the response. The 1979 article's abstract reports an early release burst followed by a slower rise. In a euglycemic insulin clamp, infused insulin is held elevated and variable glucose infusion holds blood glucose at baseline. Frequent blood sampling, a glucose analyzer, and controlled infusion apparatus make the imposed concentration a maintained condition rather than an uncontrolled consequence. ^[ref][ref]

The maintained glucose level controls an important confounder: a change in blood glucose would itself change uptake and hormone release. At a steady state, conservation of mass gives uptake equal to infused supply plus endogenous production, after accounting for losses. Consequently, infusion alone estimates uptake only if endogenous production is negligible and the other balance assumptions hold. Labelled glucose measurements can estimate residual endogenous production; matching infused insulin across comparisons matters. Whole-body uptake cannot by itself identify the responding tissue, and plasma insulin reflects both release and removal. This interpretation uses the accessible 1979 abstract and the later authored methods chapter; the original article's full methods were not available for inspection.^[ref]