title: High insulin-like growth factor-1 in patients with bipolar I disorder: a trait marker?
abstract: OBJECTIVE
  Neurotrophic factors exert substantial effects on the central nervous system. The present study investigates the roles of insulin-like growth factor-1 (IGF-1), β-nerve growth factor (β-NGF), and brain-derived neurotrophic factor (BDNF) in bipolar disorder.
  
  
  METHODS
  Baseline levels of culture-stimulated IGF-1, β-NGF, and BDNF were compared in 116 patients with bipolar I disorder and 123 healthy controls. Neurotrophic factors were also compared in patients before and after 6 weeks of pharmacotherapy. A multivariate logistic regression analysis was used to investigate the influence of the neurotrophic factors analyzed in quartile form, in relation to confounding variables, such as age, sex, and body mass index.
  
  
  RESULTS
  IGF-1 was significantly higher in patients (mean=514.57, SD=259.78) than in healthy controls (mean=316.82, SD=270.00, p<0.0001) at baseline. Furthermore, higher levels of IGF-1 substantially increased the risk for bipolar I disorder. IGF-1 level was not significantly changed at 6-weeks (mean=506.41, SD=313.66). No changes in BDNF or β-NGF-1 levels were found following the 6-week treatment period. IGF-1 and β-NGF were negatively correlated in healthy controls, but not in patients. Severity of manic symptoms was not associated with any of the neurotrophic factors.
  
  
  CONCLUSIONS
  We did not measure cortisol, growth hormone, or IGF-1 receptors. This study is cross-sectional in design.
  
  
  CONCLUSIONS
  Elevated IGF-1 levels may be a trait marker for bipolar disorder. Further studies are needed to thoroughly investigate the role of IGF-1 in relation to other neuroendocrine factors and biological markers for bipolar disorder.
authors.affiliation: Department of Psychiatry, College of Medicine, Korea University, Seoul, Republic of Korea.
authors.forename: Yong-Ku
authors.initials: YK
authors.lastname: Kim
authors.affiliation: Department of Psychiatry, Gachon University Gil Medical Center, 1198, Guwol-dong, Namdong-Gu, Incheon, Republic of Korea. Electronic address: ksna13@gmail.com.
authors.forename: Kyoung-Sae
authors.initials: KS
authors.lastname: Na
authors.affiliation: Department of Psychiatry, College of Medicine, Korea University, Seoul, Republic of Korea.
authors.forename: Jung-A
authors.initials: JA
authors.lastname: Hwang
authors.affiliation: Department of Psychiatry, College of Medicine, Korea University, Seoul, Republic of Korea.
authors.forename: Ho-Kyoung
authors.initials: HK
authors.lastname: Yoon
authors.affiliation: Department of Psychiatry, College of Medicine, Korea University, Seoul, Republic of Korea.
authors.forename: Heon-Jeong
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Department of Psychiatry, College of Medicine, Soonchunhyang University, Seoul, Republic of Korea.
authors.forename: Sang-Woo
authors.initials: SW
authors.lastname: Hahn
authors.affiliation: Department of Psychiatry, Gangnam Eulji Hospital, Eulji University, Seoul, Republic of Korea.
authors.forename: Bun-Hee
authors.initials: BH
authors.lastname: Lee
authors.affiliation: Department of Psychiatry, College of Medicine, Soonchunhyang University, Seoul, Republic of Korea.
authors.forename: Han-Yong
authors.initials: HY
authors.lastname: Jung
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D001714:Bipolar Disorder / Q000097:blood* / Q000188:drug therapy; D019208:Brain-Derived Neurotrophic Factor / Q000097:blood*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D020932:Nerve Growth Factor / Q000097:blood*; D055815:Young Adult
chemical_list: D015415:Biomarkers; D019208:Brain-Derived Neurotrophic Factor; D007334:Insulin-Like Growth Factor I; D020932:Nerve Growth Factor
keywords: Bipolar disorder; Brain-derived neurotrophic factor; Insulin-like growth factor-1; Nerve growth factor; Neurotrophin