Response of serum prolactin to exogenous stimulation

Previous observations by other workers indicating suppression of serum prolactin (hPRL) by water loading could not be confirmed. Sequential testing using an acute water load in patients with various clinical diagnoses did not aid conclusively in differentiating functional hyperlactinemic states from pituitary adenoma. It was of interest that the acute ingestion of water resulted in a triphasic response in serum hPRL levels. The response to breast stimulation was more marked in patients with excessive breast hypertrophy and galactorrhea. This was in contrast to patients with hypo- or hyperthyroidism, anorexia nervosa, and our normal subjects. In response to breast stimulation, there was no difference among the normal group, women with functional hyperlactinemia, and patients with proven pituitary adenoma. When they were compared with other patient groups in this study, marked responsiveness was found in patients with amenorrhea and galactorrhea, amenorrhea with elevated hPRL levels without galactorrhea, breast hypertrophy, and adrenal overactivity in response to these two stimuli. The physiologic mechanisms resulting in the increase in serum hPRL levels seen in these patients remain unclear at the present time.