One cause is hyperprolactinemia, or excessive prolactin secretion by pituitary lactotroph cells, which is frequently seen with a benign pituitary tumor called a prolactinoma.

一个原因是高泌乳素血症，即垂体泌乳素细胞分泌过多泌乳素，大多并发良性的垂体肿瘤，称为泌乳素瘤。