The human body is a complex system of organ systems, each one working in it's own right to produce some pliable set of goods the body needs to carry out it's life processes. The combined effort of all these organ systems working in conjunction with each other is called homeostasis. If just one of the organ systems stops functioning, or is impaired in some way, so as to slow down what it does for the body, it generally has a negative effect on the body's performance in some way.
The endocrine system is a set of organs that produce different substances called hormones. These hormones all have different target tissues within the body they act upon. The actions that are caused by these hormones are instrumental in what we would typically call good health of the body.
Psychotic behavior is a feeling of anxiety, a feeling "someone is out to get me", that is produced from no observable stressor in a person's life. A person who exhibits such behavior might have something wrong with one or more of the endocrine glands that make up the endocrine system. Too much or too little of the hormone that gland produces could be manifested in psychotic behavior.