Serum Insulin-Like Growth Factor 1 and Growth Hormone Levels of Hypoxic-Ischemic Newborns

Abstract

A number of growth factors, their binding proteins, and their receptors have been shown to be induced in the hypoxic-ischemic (HI) brain. In this prospective study, we aimed at determining the levels of insulin-like growth factor 1 (IGF-1), growth hormone (GH), and cortisol in HI babies and at identifying whether they differ from the levels of control infants. The serum IGF-1 levels were measured after the first 12–24 h of life, and the measurements were repeated on the 5th and 10th days of life for babies with HI encephalopathy (n = 18) and on the 10th day of life for controls (n = 19). Blood samples for measurement of cortisol and GH from both HI and control groups were collected after the first 12–24 h of life. There were 11 babies in the mild-to-moderate (stages I and II) group and 7 babies in the severe (stage III) group according to Sarnat and Sarnat. The IGF-1 levels of the HI group measured after 12–24 h [78.5 ± 27.9 (range 9–123.4) ng/ml] and on the 10th day [72.2 ± 36.8 (range 29.7–159.2) ng/ml] of life were statistically significantly lower than the IGF-1 levels of the control group [121.5 ± 50.4 (range 74.4–280.5) ng/ml and 133.1 ± 34.4 (range 65.9–202) ng/ml, respectively] (p = 0.002 and p = 0.001, respectively). But there was no statistically significant difference between mild-to-moderate HI group and severe HI group in terms of IGF-1 levels after 12–24 h and 5 and 10 days of life (p > 0.05). Also there was no statistically significant difference in IGF-1 values after the first 12–24 h and after 10 days of life between HI subjects who died or survived (p > 0.05). The GH levels of the HI group after the first 12–24 h of life [34.6 ± 32.3 (range 0.1–120) mIU/l] were statistically significantly higher than those in the control group [10.4 ± 4.5 (range 3.7–16.9) mIU/l] (p = 0.005). There was no statistically significant difference in the serum cortisol levels between HI and control groups after the first 12–24 h of life [18.7 ± 17.0 (range 1.6–65.1) µg/dl vs. 10.8 ± 5.4 (range 3.0–23.2) µg/dl] (p > 0.05). No statistically significant correlation was found between IGF-1 levels and GH and cortisol levels of the HI encephalopathy group [r = –0.113 (p > 0.05) and r = 0.108 (p > 0.05), respectively]. In conclusion, this study showed decreased levels of serum IGF-1 and increased levels of GH which may be secondary to serum IGF-1 influx from the circulation to the brain as a protective mechanism or may be due to some cytokines which alter the GH/IGF axis, inhibit the action of IGF-1, and stimulate IGF-binding protein 1.