ABSTRACT
This chapter aims to understand the basic principles of feedback mechanisms, and presents important examples of the relevance of feedback mechanisms in basic and clinical endocrinology and how these may be used as diagnostic tests. It provides general principles of treatment using knowledge of endocrine feedback systems. Feedback systems maintain a set point for example central heating temperature regulation. Biological feedback mechanisms also control: fertility, metabolism, poorly understood cycles of sleep and wakefulness and circadian and other rhythms. Endocrine feedback systems include control of: brain and pituitary hormones, adrenal hormones, gastrointestinal tract hormones, growth hormones, sex hormones, thyroid hormones, feeding and satiety hormones, and salt and water balance. Many endocrine diseases result from disturbances of feedback control systems, and tests of feedback systems are of diagnostic value in, for example: acromegaly, Addison's disease, Cushing's disease, diabetes mellitus, growth disorders, hypo- or hyperthyroidism, infertility, and obesity.
