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) mug/dl vs. 10.8 +/- 5.4 (range 3.0 - 23.2) mug/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. Copyright (C) 2004 S. Karger AG, Basel.