Prolactinoma
Prolactinoma is a benign tumor arising from the anterior pituitary that secretes excess prolactin (a pituitary neuroendocrine tumor, PitNET). It is the most common functional pituitary tumor and is markedly more frequent in women than men. Unlike other pituitary tumors, its first-line treatment is medical therapy with dopamine agonists rather than surgery.
最終更新: 2026-06-07
Definition
Prolactinoma is a benign tumor originating from the lactotroph cells of the anterior pituitary (adenohypophysis) that secretes prolactin. Since the 2022 WHO classification of pituitary tumors, the term 'pituitary neuroendocrine tumor (PitNET)' is used in place of 'pituitary adenoma'; prolactinoma is defined as a PIT1-lineage PitNET. It makes up a large proportion of all functional pituitary tumors.
Epidemiology
Prolactinoma is the most common functional pituitary tumor. It is roughly ten times more frequent in women than in men. In women it is most often diagnosed during reproductive age (20-40 years); in men, because symptoms are noticed later, diagnosis usually comes at an older age and with a larger tumor. The female predominance reflects the stimulating effect of estrogen on lactotroph cells.
Symptoms
Symptoms arise from the hormonal effects of high prolactin and, in large tumors, from mass effect. In women the most common features are menstrual irregularity or absence (amenorrhea/oligomenorrhea), milky nipple discharge (galactorrhea), infertility and reduced libido. In men, loss of libido, erectile dysfunction and infertility predominate; because these are non-specific, diagnosis may be delayed. Large tumors (macroprolactinomas) can cause visual field loss from optic chiasm compression (bitemporal hemianopsia), headache and deficiency of other pituitary hormones (hypopituitarism).
Classification
Prolactinomas are classified by size. A microprolactinoma is smaller than 10 mm and is the most common form, particularly in women, because early hormonal symptoms lead to early diagnosis. A macroprolactinoma is 10 mm or larger; it is more often seen in men, with higher prolactin levels, and may produce significant mass effect. The rare giant prolactinoma is 40 mm or larger and is characterized by very high prolactin levels and aggressive local growth.
Diagnosis
The most important test is the serum prolactin level, which generally correlates with tumor size; very high values suggest a macroprolactinoma. In very large tumors, the 'hook effect'—a falsely low reading due to assay technique—must be considered. Other causes of raised prolactin, such as pregnancy, certain medications (especially antipsychotics and anti-nausea drugs), hypothyroidism and renal or hepatic failure, should be excluded. Contrast-enhanced pituitary MRI is the gold standard for imaging the tumor; in macroprolactinoma, visual field testing and assessment of other pituitary hormones are required.
Treatment Options
Unlike other pituitary tumors, first-line treatment for prolactinoma is dopamine agonist medication rather than surgery. Cabergoline is considered the gold standard in most cases; it largely normalizes prolactin and shrinks the tumor, with the advantages of twice-weekly dosing and good tolerability. Bromocriptine is an alternative and may be preferred when pregnancy is planned. Medical treatment is usually continued for at least several years; follow-up is needed because recurrence can occur after stopping. Surgery (an endoscopic transsphenoidal approach) is considered for drug resistance or intolerance, acute visual loss, or bleeding into the tumor. In resistant or aggressive cases, radiotherapy and, in selected cases, additional treatments such as temozolomide may be considered.
Prognosis
Prolactinoma is a benign tumor that does not metastasize, and the response to treatment is usually very good. In the large majority of cases, medical therapy normalizes prolactin, shrinks the tumor and relieves symptoms, with fertility often restored in women. Untreated large tumors may lead to permanent visual loss, hypopituitarism and bone loss. Care is planned by a team including endocrinology and neurosurgery; outcomes vary from patient to patient and no outcome can be guaranteed.
参考文献
- Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th ed. Thieme; 2023:861-873.
- Winn HR, ed. Youmans Neurological Surgery. 6th ed. Saunders; 2011:1481-1509.
- Osborn AG, Hedlund GL, Salzman KL. Osborn's Brain: Imaging, Pathology, and Anatomy. 2nd ed. Elsevier; 2018:795-807.
- Melmed S, et al. Diagnosis and Treatment of Hyperprolactinemia: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2011.
- Petersenn S, et al. Diagnosis and management of prolactin-secreting pituitary adenomas: a Pituitary Society consensus statement. Nat Rev Endocrinol. 2023.
本項目は一般的な情報提供を目的としており、医師の診察に代わるものではありません。診断と治療の判断は個々の状況によります。