Which pituitary adenoma secretes excessive prolactin?

• A. Corticotroph adenomas
• B. Prolactinomas
• C. Somatotroph adenomas
• D. Thyrotroph adenomas

Answer: (B)

Lactotrophs in the anterior pituitary are the cells that produce prolactin, so when a pituitary tumor arises from these cells, it overproduces prolactin. This excess prolactin suppresses GnRH, which lowers LH and FSH and leads to reproductive symptoms such as menstrual irregularities and galactorrhea in women and reduced libido or infertility in men. Other pituitary adenomas secrete different hormones: corticotroph tumors make ACTH (often causing Cushing disease), somatotroph tumors make growth hormone (causing acromegaly or gigantism), and thyrotroph tumors make TSH (leading to hyperthyroidism). Clinically, when hyperprolactinemia is present, the suspicion for a prolactin-secreting tumor is high. Diagnosis commonly involves a serum prolactin level and MRI of the pituitary, and treatment typically starts with dopamine agonists (like cabergoline or bromocriptine), which lower prolactin levels and often shrink the tumor.