Nerve growth factor serum concentrations in healthy human volunteers: physiological variance and stability.

Human nerve growth factor (NGF) serum concentrations were measured in a healthy sample of 126 participants by a modified highly sensitive and specific two-site enzyme immunoassay. The measured NGF concentrations differ considerably from a normal distribution. The median NGF concentration was 19.68 pg/ml with an interquartile range of 11.06-41.74 pg/ml, which means that 50% of the NGF levels are in this range. In our healthy sample, we found no gender differences but a slight age-related decrease of NGF (r=-0.1326, P=0.1560). Moreover intraindividual stability of NGF was examined in ten volunteers, where no significant changes of serum NGF concentrations were detected over 4 weeks. This stability of our repetitive measurements over 4 weeks suggests that this neurotrophin may be an intraindividually solid marker at least in human serum.