A review is presented of the endocrine status in human obesity. The effect of changes in nutrient intake or body weight and the use of weight-reducing drugs on endocrine systems are discussed. There are several endocrine abnormalities found in obese patients. However, these altered endocrine functions seem secondary to the obese state and do not play a role in the pathogenesis of obesity. Some of these abnormalities are, at least partially, responsible for the development of complications related to the obese state. Weight reduction in general is followed by normalization of endocrine functions. The pharmacological agents used in the treatment of obesity do not influence the endocrine systems significantly.