Effect of insulin treatment on circulating insulin‐like growth factor I and IGF‐binding proteins in cats with diabetes mellitus

Background Insulin‐like growth factor‐I (IGF‐I) is used to screen for acromegaly in diabetic cats. In humans, most circulating IGF‐I forms ternary complexes (TC) with IGF‐binding protein (IGFBP‐3) and an acid‐labile subunit. Compared to humans, the amount of TC in cats is more variable. Insulin‐like growth factor‐I concentrations are reported to increase during insulin treatment, more rapidly in cats achieving remission. Objectives To investigate (i) factors associated with circulating IGF‐I concentrations, including IGFBP‐profiles (ii) effect of insulin treatment on IGF‐I concentrations and (iii) IGF‐I as prognostic marker of diabetes mellitus remission. Animals Thirty‐one privately owned diabetic cats of which 24 were followed 1 year, and 13 healthy cats. Methods Prospective study. Serum insulin, IGF‐I, glucose, and fructosamine concentrations were measured. IGF‐binding forms were determined by chromatography in 14 diabetic and 13 healthy cats; and IGF‐I, IGF‐II, IGFBP‐3, and IGFBP‐5 by mass spectrometry in 3 cats achieving remission. Results Insulin‐like growth factor‐I median (interquartile range) before start of insulin treatment was 300 (160‐556) ng/mL. Insulin‐like growth factor‐I was positively associated with TC (P