you're example assumes you know what causing the problem though. This is far, far from the case here - "Down syndrome causes decrease in GnRH" does not imply "L

you're example assumes you know what causing the problem though. This is far, far from the case here - "Down syndrome causes decrease in GnRH" does not imply "Low GnRH causes down syndrome", though as I said, if you get lucky it could be responsible for a good number of the symptoms.