Diminished Prolactin Response to Thyrotropin and Insulin in Anorexia Nervosa

Although patients with anorexia nervosa (AN) have a variety of endocrine disturbances, it generally is believed that the PRL response to stimulation is not altered in this disorder. We measured basal serum PRL values and serum PRL values after stimulation either with TRH (200 micrograms/m2) or with insulin (4 IU/m2) in 27 women with AN and 9 normal women. Basal values in anorexic women and normal women did not differ significantly, whereas all stimulation variables (mean PRL stimulation values, maximum PRL values, sum of increments, and area under the stimulation curve) were significantly lower in AN patients than in normal women. Furthermore, after TRH stimulation most of these variables correlated positively with the percentage of ideal body wt of the patients, indicating that the diminished PRL response was wt dependent. This diminished PRL response in the patients may accompany starvation and low estradiol values. Both conditions per se are known for their association with diminished PRL responses. Hence, no hypothesis which posits hypothalamic dopamine excess as the basic disturbance in AN seems justified. Moreover, diminished PRL responses in AN are not consistent with an assumption of hypothalamic dopamine depletion in this disorder.