Growth hormone releasing factor in human cerebrospinal fluid

Growth hormone releasing factor (GHRF) was determined by radio-immunoassay in cerebrospinal fluid (CSF) from 37 unmedicated healthy volunteers (mean ± SD = 23.4 ± 7.2 pg/ml). A second lumbar puncture in 11 of these subjects suggested that the CSF GHRF levels were stable over time. High performance liquid chromatography revealed that the CSF immunoreactivity co-eluted with the 1-44NH₂ and 1-4ONH₂ forms of GHRF. Measurements of GHRF in sequential CSF aliquots revealed no evidence of a rostro-caudal gradient, an observation that is compatible with the hypothesis that GHRF has a long half-life in CSF. A significant negative correlation with body weight was found in the 37 subjects. Levels of CSF GHRF were determined in 24 lithium-treated euthymic bipolar patients, 13 of whom provided a second CSF sample during the unmedicated state. No group differences or effects of lithium were noted.