spina-gr spina-gr spina-gr is a calculated biomarker for insulin sensitivity. it represents insulin receptor gain. spina-grcalculatorhttps://doi.org/10.5281/zenodo.7479856purposemedical diagnosis, researchtest ofinsulin sensitivity how to determine gr the index is derived from a mathematical model of insulin-glucose homeostasis. for diagnostic purposes, it is calculated from fasting insulin and glucose concentrations with: g ^ r = g 1 p ( ∞ ) ( d r + [ i ] ( ∞ ) ) g e [ i ] ( ∞ ) [ g ] ( ∞ ) − d r g e [ i ] ( ∞ ) − 1 g e _=_p(\infty )(_+\left(\infty ))}_\left(\infty )(\infty )}}-__(\infty )}}-_ . (∞): fasting insulin plasma concentration (μu/ml) (∞): fasting blood glucose concentration (mg/dl) g1: parameter for pharmacokinetics (154.93 s/l) dr: ec50 of insulin at its receptor (1,6 nmol/l) ge: effector gain (50 s/mol) p(∞): constitutive endogenous glucose production (150 µmol/s) clinical significance validity compared to healthy volunteers, spina-gr is significantly reduced in persons with prediabetes and diabetes mellitus, and it correlates with the m value in glucose clamp studies, triceps skinfold, subscapular skinfold and (better than homa-ir and quicki) with the two-hour value in oral glucose tolerance testing (ogtt), glucose rise in ogtt, waist-to-hip ratio, body fat content (measured via dxa) and the hba1c fraction. pathophysiological implications in lean subjects it is significantly higher than in a population with obese persons.