IGF-I levels in the cerebrospinal fluid in patients with acromegaly

IGF-I (Insulin like growth factor-I) plays a definitive role in the central nervous system (CNS) by modulating neuronal regeneration and survival. The local production of IGF-I in CNS has been demonstrated, but the contribution of circulating IGF-I transported through blood-brain barrier (BBB) has been just suggested in animals. There is currently no data available concerning IGF-I transport in CNS in humans. In order to investigate the passage of IGF-I over BBB in humans we have simultaneously measured the IGF-I and GH levels in serum and CSF in 25 patients with active acromegaly. IGF-I and GH levels in CSF were lower than in serum (2.2 +/- 0.24 ng/mL vs 686.6 +/- 46.83 ng/mL for IGF-I and 2.13 +/- 0.627 mU/l vs 58.8 +/- 15.86 mU/L for GH). However, both IGF-I and GH serum levels correlated with their CSF levels (r= 0.4, p < 0.05 for IGF-I and r= 0.651, p= 0.006 for GH), suggesting that BBB is permeable for both hormones. In conclusion, we demonstrate the correlation of the IGF-I levels in serum and CSF, providing indirect evidence for IGF-I passage through BBB.