7 women and 3 men with anorexia nervosa were tested with thyrotropin-releasing hormone (TRH) and luteinizing hormone-follicle stimulating hormone-releasing hormone (LH-RH) and the growth hormone (GH), prolactin (PRL), gonadotropin (FSH-LH) and thyrotropin (TSH) responsiveness of their anterior pituitaries (AP) to the two hypothalamic neurohormones were determined. Administration of TRH (500 microgram i.v.) induced rises in plasma GH in 4 patients, while in 4 patients it induced rises in plasma FSH and/or LH. LH-RH (150 microgram i.v.) induced rises in plasma GH in 3 patients, increased plasma PRL in 3 patients and plasma TSH in 1 patient. Collectively, in only 1 patient, who was in a phase of initial nutritional rehabilitation, was there conventional AP responsiveness to hypothalamic neurohormones. This demonstrates that there is a profound derangement of AP responsiveness to hypothalamic neurohormones in patients with anorexia nervosa, probably reflecting a primary alteration in brain neurotransmitter function.