Hi..... Excessive prolactin can cause a decrease in sex hormones like estrogen. When you have excessive amounts of prolactin in your blood it is called hyperprolactinemia. This is sometimes a marker of a condition known as prolactinoma, which is a tumor of the pituitary gland (usually non-cancerous). Prolactinomas produce higher than normal levels of prolactin, which can act on the body and produce many PCOS-like symptoms....