Evaluation of serum insulin-like growth factor 1 concentrations in non-diabetic cats with chronic kidney disease

Feline hypersomatotropism (HST) can develop in both diabetic and non-diabetic cats, but studies evaluating the prevalence of HST in cats without diabetes mellitus (DM) are lacking. The aims of the study were to evaluate circulating insulin-like growth factor 1 (IGF-1) in non-diabetic cats with chronic kidney disease (CKD), to assess whether there is a correlation between general test of renal function and IGF-1 concentration in cats with CKD, and to screen this population for the presence of HST. In this prospective study, one hundred fifty-four non-diabetic cats (n = 154) with CKD from referral centers in Buenos Aires (Argentina) were evaluated. Serum IGF-1 concentration was measured as part of the routine tests for CKD and compared with a healthy control group of 50 cats without CKD. The median serum IGF-1 concentration in the total population of cats with CKD was 500 ng/mL (range 34-1593 ng/mL). Median serum IGF-1 concentrations of cats with IRIS stage 1 (n = 13), stage 2 (n = 86), stage 3 (n = 40) and stage 4 (n = 15) of CKD were 230 ng/mL (range 58-951 ng/mL), 473 ng/mL (range 34-1456 ng/mL), 597 ng/mL (range 123-1593 ng/mL), 569 ng/mL (range 123-1045 ng/mL), respectively. None of the cats in the control group had IGF-1 concentration >1000 ng/mL (median 505 ng/mL, range 114-720 ng/mL). There was a positive linear correlation between serum IGF-1 and creatinine concentrations in cats with CKD (r= 0.22, 95% confidence interval 0.06-0.37 P=0.005). A proportion of 5.8% (95% confidence interval 2.7-10.8%) of non-diabetic cats with CKD had markedly increased IGF-1 concentrations (cut-off IGF-1 >1000 ng/mL). Pituitary enlargement was detected on computed tomography in 3/4 of these cases. Eighteen cats (11.6%) had serum IGF-1 concentrations in the "grey zone" between 800 and 1000 ng/mL. A small proportion of non-diabetic cats with CKD had an IGF-1 concentration in a range that is consistent with HST in diabetic cats. Likewise, the progression of CKD in cats without DM correlates with increases in serum IGF-1 concentrations.