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 interval in a large population-based study of diabetes in southern Wisconsin. Participants included people with younger-onset diabetes (n = 66 adolescents, n = 661 adults > or = 18 years of age) and older-onset diabetes (n = 285 for those using insulin, n = 248 for those not using insulin). Fundus photographs were graded in a masked fashion using standardized protocols to determine the severity of retinopathy in each eye. Serum IGF-I levels were measured during 1984-1986 using a double-antibody radioimmunoassay. Mean IGF-I was highest in adolescents (499.1 micrograms/l), lower in younger-onset adult (280.1 micrograms/l), and lowest in the older-onset group (205.7 and 221.2 micrograms/l for older-onset group using insulin and not using insulin, respectively). The incidence of retinopathy was not significantly higher in people with higher IGF-I levels in
