Hyperprolactinemia is an abnormally high level of prolactin in the blood due to hypersecretion of prolactin from lactotroph cells in the pituitary gland due to physiologic or pathologic causes. There is a predisposition in women. This hypersecretion may result from a prolactin-secreting tumor (prolactinoma), pregnancy, medications (typically antipsychotic drugs or other medications that inhibit dopamine), or a large pituitary tumor.

Clinical presentation is variable. Female patients most commonly present with oligomenorrhea, amenorrhea, reduced libido, or infertility (resulting from prolactin suppression of gonadotropin-releasing hormone [GnRH]). Galactorrhea in females may occur as a result of the physiologic effect of prolactin on breast epithelial cells. Male patients most commonly present with loss of libido, visual impairments, or headache. Decreased serum testosterone levels and hypogonadism in males may occur due to a decrease in luteinizing hormone (LH) and follicle-stimulating hormone (FSH) resulting from prolactin suppression of GnRH. In both male and female patients, a pituitary tumor may cause visual-field defects and headache.

Complications include osteoporosis, which may result from decreased gonadal steroid secretion.