"Zinc-treated patients had significantly lower serum prolactin levels (11 +/- 4 ng/ml v 29 +/- 7 ng/ml) than untreated patients."
Effect of zinc supplementation on hyperprolactinaemia in uraemic men - PubMed
Zinc and prolactin levels were measured in 32 male haemodialysis patients; 12 were receiving 50 mg zinc per day as zinc acetate and 20 were not. Zinc-treated patients had significantly higher plasma zinc levels (134 +/- 10 micrograms/dl v 88 +/- 2 micrograms/dl) and lower serum prolactin levels...
pubmed.ncbi.nlm.nih.gov