Ciliary neurotrophic factor (CNTF) is a nerve growth factor which promotes differentiation into astrocytes. In 2001, it was reported that in a human study examining the usefulness of CNTF for treatment of motor neuron disease, CNTF produced an unexpected and substantial weight loss in the study subjects. Further investigation revealed that CNTF could reduce food intake without causing hunger or stress, and is believed to operate by a non-leptin, but 'leptin-like' pathway.