DOES INSULIN-LIKE GROWTH-FACTOR-I PREDICT INCIDENCE AND PROGRESSION OF DIABETIC-RETINOPATHY

We evaluated the relationship of insulin-like growth factor (IGF)-I to incidence and progression of diabetic retinopathy over a 6-year inter val in a large population-based study of diabetes in southern Wisconsi n. Participants included people with younger-onset diabetes (n = 66 ad olescents, n = 661 adults greater than or equal to 18 years of age) an d older-onset diabetes (n = 285 for those using insulin, n = 248 for t hose not using insulin). Fundus photographs were graded in a masked fa shion using standardized protocols to determine the severity of retino pathy in each eye. Serum IGF-I levels were measured during 1984-1986 u sing a double-antibody radioimmunoassay. Mean IGF-I was highest in ado lescents (499.1 mu g/l), lower in younger-onset adults (280.1 mu g/l), and lowest in the older-onset group (205.7 and 221.2 mu g/l for older -onset group using insulin and not using insulin, respectively). The i ncidence of retinopathy was not significantly higher in people with hi gher IGF-I levels in any group. The odds of developing diabetic retino pathy in 6 years for each 10 mu g/l increase in IGF-I after controllin g for age, glycosylated hemoglobin, and duration of diabetes at baseli ne was 1.21 (95% confidence interval [CI] 0.95-1.54) for adolescents; 1.00 (95% CI 0.93-1.08) for younger-onset adults; 0.93 (95% CI 0.85-1. 02) for the older-onset group using insulin; and 0.99 (95% CI 0.95-1.0 4) for the older-onset group not using insulin. In summary, IGF-I was not associated with 6-year incidence or progression of diabetic retino pathy in any of the groups.