Prolactinoma

Prolactinoma is the most common type of functioning pituitary adenoma, a benign tumor of the anterior pituitary gland that produces excessive amounts of the hormone prolactin (hyperprolactinemia). Also known as lactotroph adenoma or prolactin-secreting pituitary adenoma, this tumor primarily affects the endocrine and reproductive systems. Prolactinomas are classified by size as microprolactinomas (less than 10 mm in diameter) or macroprolactinomas (10 mm or larger). Microprolactinomas are more common in women, while macroprolactinomas are more frequently diagnosed in men. The hallmark of prolactinoma is elevated prolactin levels, which leads to a range of clinical features. In women, key symptoms include amenorrhea (absence of menstrual periods), oligomenorrhea (irregular periods), galactorrhea (abnormal breast milk production), infertility, and decreased libido. In men, symptoms include erectile dysfunction, decreased libido, gynecomastia, and infertility. Because symptoms in men are often subtle, macroprolactinomas are more commonly found at diagnosis in males, and these larger tumors can cause mass effects such as headaches, visual field defects (particularly bitemporal hemianopia due to compression of the optic chiasm), and hypopituitarism from compression of surrounding normal pituitary tissue. Long-standing hyperprolactinemia in both sexes can lead to decreased bone mineral density and osteoporosis. The treatment landscape for prolactinoma is well established. First-line therapy consists of dopamine agonists, primarily cabergoline and bromocriptine, which effectively reduce prolactin levels and shrink tumor size in the majority of patients. Cabergoline is generally preferred due to its superior efficacy and better side-effect profile. Surgical intervention (transsphenoidal surgery) is reserved for patients who are resistant to or intolerant of dopamine agonists, or in cases of acute visual compromise. Radiation therapy is rarely needed and is considered a third-line option. Most prolactinomas are sporadic, though a small proportion occur as part of hereditary syndromes such as Multiple Endocrine Neoplasia type 1 (MEN1) or Familial Isolated Pituitary Adenoma (FIPA), the latter sometimes associated with AIP gene mutations.

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