Prolactin Stimulation by Meals Is Related to Protein Content*

To study the effect of meals on PRL secretion, serum PRL was measured after the ingestion of mixed meals and specific single macronutrients by normal men and women. In men, only protein feeding significantly stimulated PRL secretion. In women, protein meals as well as a standard mixed meal and a liquid mixed meal resulted in PRL release. Fat, glucose, and a nonnutrient meal had no consistent effect on serum PRL. Serum TSH was not altered by any of the meals, and serum GH and cortisol showed few changes. We conclude that PRL stimulation by meals may be of occasional clinical significance, principally in confusing the diagnosis of hyperprolactinemic states, especially in women. Dietary protein is probably the agent responsible for PRL secretion induced by meals.