Nine patients (4F, 5M) aged 12-17 years with“fear of obesity”were studied with a sequential stimulation test utilizing insulin, LRH, TRH, and L-dopa. The comparative groups were nine female with classic anorexia nervosa, five males with undifferentiated nutritional dwarfing, and nine children (1F, 8M) with constitutional growth delay. The serum TSH, glucose, cortisol, somatotropin, prolactin, LH, and FSH were sampled periodically over 2 hours. Basal T3, T4, transferrin, and Somatomedin-C levels were also obtained. The“fear of obesity”patients did not have any pituitary function changes that were unique. These patients, as well as the comparison groups, revealed a delayed TSH response in proportion to the weight deficit which, when expressed as an integrated response, correlated well to the weight deficit for height (P less than 0.001) and to the ability to recover from hypoglycemia (p less than 0.001). The Somatomedin-C level was low and correlated to the T3 level (p less than 0.05) and not correlated to the elevated Somatotropin levels. The pituitary response to combined stimulation in patients with fear of obesity was determined to be a component of the spectrum starting at normal and proceeding to the extreme undernutrition of anorexia nervosa. Pituitary responsiveness, therefore, changes not as a function of the etiology of the malnutrition, but simply as a function of its severity.