HCRT and hypocretin deficiency: To test whether IGFBP3 activity regulates hypocretin levels in vivo, DNA samples of 262 Caucasian subjects with normal CSF hypocretin-1 levels (>200 pg/ml), either drawn from healthy control subjects or from subjects with a complaint of sleepiness unexplained by hypocretin deficiency, were typed for rs2854744 (−202A/C IGFBP3 promoter polymorphism).