Prolactinomas are the most common hormone-secreting pituitary tumors. It is a noncancerous (benign) pituitary tumor that produces a hormone called prolactin. This results in too much prolactin in the blood. These occur most commonly in people under age 40. They are about five times more common in women than in men, but are rare in children. Larger tumors are more common in men. They tend to occur at an older age. The tumor can grow to a large size before symptoms appear.
Symptoms: When prolactin levels get increased there will be no periods, milk production will occur (infrequent in men), loss of axillary and pubic hair and Small gonads, gynecomastia, erectile dysfunction (in males). When there is mass effect then, bitemporal hemianopsia (due to pressure on optic chiasm), vertigo, nausea, vomiting are the symptoms.
Cause: A prolactinoma occurs when the cells that are responsible for the production of the hormone prolactin (known as lactotroph cells) start to multiply for no apparent reason. This can lead to the development of a growth of variable size within the pituitary gland. The majority of prolactinomas are less than 1cm in size. The increase in number of prolactin producing cells leads to excess production of the hormone prolactin, leading to high levels in the blood