A rare genetic endocrine disorder characterized by persistently high prolactin serum levels (not associated with gestation, puerperium, drug intake or pituitary tumor) in multiple affected family members. Clinically it manifests with signs usually observed in hyperprolactinemia, which are: secondary medroxyprogesterone acetate (MPA)-negative amenorrhea and galactorrhea in female patients, and hypogonadism and decreased testosterone level-driven sexual disfunction in male patients. Oligomenorrhea and primary infertility have also been reported in some female patients.