Serum insulin-like growth factor-1 concentrations in healthy cats before and after weight gain and weight loss.

Abstract

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&#x2009;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&#x2009;&#xb1;&#x2009;0.4 kg) to week 40 (6.5&#x2009;&#xb1;&#x2009;1.2 kg) (P&#x2009;<&#x2009;.001) and decreased by 25% from week 40 to week 60 (4.9&#x2009;&#xb1;&#x2009;0.7 kg) (P&#x2009;<&#x2009;.001). Serum IGF-1 concentrations did not differ during the study period (week 0, 16, 40, 60: 500&#x2009;&#xb1;&#x2009;188, 479&#x2009;&#xb1;&#x2009;247, 470&#x2009;&#xb1;&#x2009;184, 435&#x2009;&#xb1;&#x2009;154&#x2009;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.