A variety of endocrine dysfunctions have been reported for anorexia nervosa, protein caloric malnutrition, and depression. The effect of reduced caloric intake and weight loss on endocrine functions was assessed in an experiment with five healthy female subjects during an initial baseline phase, a 3-week phase of complete food abstinence, weight gain to the original level, and a final baseline phase. During fasting, disturbances in hypothalamic-pituitary-adrenal function were observed, with elevated plasma cortisol levels, increase in the number of secretory episodes, increase in cortisol plasma half-life, and insufficient suppression following 1.5 mg dexamethasone. While all dexamethasone suppression tests (DSTs) were normal at baseline, 7 of 14 DSTs showed insufficient suppression in the fasting phase. During fasting, basal thyroid-stimulating hormone (TSH) values were lowered and the TSH response to thyrotropin-releasing hormone (TRH) was blunted. The plasma level of growth hormone (GH) over 24 hours was elevated during fasting and administration of the alpha 2-adrenergic receptor agonist clonidine resulted in a subnormal GH response after restoration of original body weight. One of the five subjects showed increased irritability, distress, anxiety, and depression as measured by various psychological scales. The results show that reduced caloric intake, weight loss, or catabolic state have powerful effects on several endocrine systems. The specificity of measures of endocrine disturbances (DST, TRH tests, and clonidine tests) as biological markers for certain types of depression must be questioned, and the metabolic state should be given more consideration in future studies.