Chapter 16 - Prolactinoma

Abstract

Prolactinomas account for approximately 50% of all pituitary adenomas coming to medical attention and are an important cause of hypogonadism and infertility. They may also be responsible for mass effects. Nevertheless, prolactinomas are not the only case of hyperprolactinemia: many physiological and pathological conditions (pregnancy, medications, pituitary stalk compression…) may be associated with hyperprolactinemia and need to be excluded by a careful history and physical examination, as well as routine blood chemistry and thyroid function testing before performing pituitary MRI. Molecular mechanisms underlying most cases of prolactinomas have not been fully defined. Some of the alterations and pathophysiologic mechanisms that have been reported are observed in several or all of the pituitary lineages, while other pathways restraining pituitary tumor growth and progression are lineage-specific. The ultimate goal of therapy for prolactinomas is restoration or achievement of eugonadism, through the normalization of hyperprolactinemia, and reduction of tumor mass. Medical therapy with dopamine agonists (DAs), particularly with cabergoline, is highly effective in the majority of cases and represents the mainstay of therapy, even though recent concerns have been raised on potential cardiac valve alterations during very high-dose and prolonged treatment. Successful withdrawal of cabergoline with maintenance of normoprolactinemia may be possible in selected circumstances. Transphenoidal, endoscopic removal of microprolactinomas may be a therapeutic option as it is very effective while for macroprolactinomas medical treatment with DAs is generally preferred, particularly when adenomas are large and/or invasive. Challenging situations, such as those encountered with resistance to DAs, giant, atypical or malignant prolactinomas, may require multimodal therapy involving surgery, radiotherapy, or both.