Prolactinoma

Source:  Pr Albert BECKERS, Dr Adrian DALY. Orphanet

Prolactinoma is a usually benign tumor of the pituitary gland that results in hyperprolactinemia.
Prolactinomas induce galactorrhoea, amenorrhoea and infertility in women, and hypogonadism, sexual dysfunction, impotence, infertility and, more rarely, gynecomastia in men.

Prolactin

Prolactin is a hormone released by the pituitary gland. This hormone stimulates secretion of breast milk.
Pregnant women have high levels of prolactin. 
Many medicines can cause prolactin levels to increase.
Hyperprolactinemia is a condition of too much prolactin in the blood of women who are not pregnant and in men.A pituitary tumor (just below the brain) called prolactinoma can cause hyperprolactinemia
It can change or stop ovulation (the release of an egg from the ovary).
In men, high prolactin levels can cause galactorrhea, impotence (inability to have an erection during sex), reduced desire for sex, and infertility. 
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