It is well known that with aging, sperm production declines as does testosterone secretion. This study does not explain what was the mechanism of action of cyproheptadine, but I would not be surprised if it resulted in increased testosterone production as well by opposing serotonin and cortisol.
http://www.ncbi.nlm.nih.gov/pubmed/1204806
http://www.ncbi.nlm.nih.gov/pubmed/1204806