Hyperprolactinemia and Prolactinoma

Prolactin is released from lactotroph cells in the anterior pituitary. Hypothalamic dopamine normally acts as a continuous brake on these cells through D2 receptors. A prolactinoma is a lactotroph adenoma that produces prolactin autonomously and may enlarge within the sella. Excess prolactin suppresses gonadotropin-releasing hormone. Luteinizing hormone and follicle-stimulating hormone then fall, reducing ovarian or testicular sex-hormone production. The resulting hypogonadism explains the common presentation: menstrual irregularity or amenorrhea, infertility, reduced libido, erectile dysfunction, and, over time, reduced bone density. Galactorrhea may occur but is not required for the diagnosis. Tumour size changes the clinical picture. A lesion extending upward can compress the optic chiasm, producing loss of peripheral visual fields. Headache, diplopia, or other cranial nerve symptoms suggest local mass effect rather than isolated hormone excess. Hyperprolactinemia is therefore a laboratory finding with several possible causes; it is not, by itself, proof of a prolactinoma.