Serum Insulin-Like Growth Factor-1 Concentrations In Healthy Cats Before And After Weight Gain And Weight Loss

Background Measurement of serum concentrations of insulin-like growth factor (IGF)-1 is used to diagnose acromegaly in cats.Hypothesis Changes of body weight do not affect serum concentrations of IGF-1 in cats.Animals Ten healthy purpose-bred cats.Methods Prospective study. In lean cats, food availability was stepwise increased during the first week and given ad libitum for a total of 40 weeks to increase their body weight. From week 41 to week 60, food access was limited to reach a weight loss of 1% to 2% each week. Measurement of IGF-1 was performed at week 0, 16, 40, and 60. Insulin-like growth factor-1 was measured by radioimmunoassay. Body weight and IGF-1 were compared among the 4 time points.Results Body weight increased by 44% from week 0 (4.5 +/- 0.4 kg) to week 40 (6.5 +/- 1.2 kg) (P < .001) and decreased by 25% from week 40 to week 60 (4.9 +/- 0.7 kg) (P < .001). Serum IGF-1 concentrations did not differ during the study period (week 0, 16, 40, 60: 500 +/- 188, 479 +/- 247, 470 +/- 184, 435 +/- 154 ng/mL, respectively; P = .38). Correlations with body weight were not observed.Conclusions and Clinical Importance Insulin-like growth factor-1 might not be influenced by changes of body weight in healthy cats, possibly suggesting that the latter is unimportant when interpreting IGF-1 results in this species.