In attacking the problem of the relationship of endocrine function to the schizophrenias and other mental diseases, we have avoided the elementary conception that certain hormones are responsible for special psychological traits and have reached the following conclusions. First, the quality of the mental disturbance depends mainly on a genetically conditioned personality pattern, various individuals reacting in different ways to the precipitating causes. Second, the hormones come into the whole picture only in so far as the hormone equilibrium of the body determines how far the individual can adjust himself to the increased demands arising out of the occurrence of various precipitating causes (Reiss, 1955). It is therefore understandable that very many, or even the majority of people suffering from severe endocrine disturbance, need not necessarily show any psychopathological changes, since their personality pattern is not so conditioned and no increased demands for adjustment are made by the occurrence of precipitating causes. On the other hand, it is equally understandable that certain disturbances in hormone production and equilibrium, even when clinically obscure, can be decisive for mental breakdown in individuals with the appropriate personality pattern, at the occurrence of precipitating causes.