Starting with the isolation and purification of human prolactin, several studies have been conducted in order to understand prolactin (PRL) physiology and pathology in the human. Results of research effected since then have shown that high levels of PRL could cause sterility either through its effects on ovulation at the hypothalamic, hypophyseal or gonadal level or through the inhibition of steroid synthesis in the ovaries which leads to amenorrhea. In parallel with these findings, bromocriptine, a dopamin agonist inhibiting PRL secretion has been used in the clinic for the treatment of hyperprolactinemic states and the positive results obtained confirmed the role of PRL in human reproduction. The aim of our study is to investigate the causative mechanisms of sterility in hyperprolactinemic patients. For this purpose, in hyperprolactinemic cases with sterility a possible correlation between the PRL values and endometrial changes is investigated. Our findings indicate that effects of PRL on the receptors of distal organs show individual variations and depend on the degree of receptor sensitivity. It is believed that the effects of PRL through receptor mediation deserve further investigation.