Prolactinoma

Prolactinomas are classified on a clinical basis by size—microadenomas are defined as less than 10 mm in diameter; macroadenomas are greater than 10 mm in diameter. Giant prolactinomas are defined as greater than 4 cm in diameter and those with more than 2 cm of suprasellar extension. Supra-, infra- and parasellar extension occur when adenomas grow beyond the immediate sellar region. Coincident with the initial characterization of prolactin (PRL) in the early 1930s by Riddle and his colleagues were the first clinical reports of a syndrome of amenorrhea coupled with galactorrhea. However, it was not until 1972 that Friesen et al. first demonstrated elevated PRL levels in the serum of a patient with a prolactinoma, the decline in such levels with partial adenomectomy, and the production of PRL by the tumor in vitro. Over the ensuing years, improvements in diagnostic radiologic procedures, advances in surgical techniques and the development of dopamine agonists as medical therapy have resulted in highly successful rates of treatment for the majority of prolactinomas. Prolactinomas are the most common subtype of the hormone-secreting pituitary tumours according to autopsy, epidemiological and surgical series.