Pituitary adenomas are common benign monoclonal
neoplasms accounting for about 15% of
intracranial neoplasms. Data from postmortem studies and imaging studies suggest that 1 of 5 individuals in the general population may have
pituitary adenoma. Some
pituitary adenomas (mainly microadenomas which have a diameter of less than 1 cm) are exceedingly common and are incidentally diagnosed on magnetic resonance imaging (MRI) performed for an unrelated reason (
headache,
vertigo,
head trauma). Most microadenomas remain clinically occult and stable in size, without an increase in
tumor cells and without local mass effects. However, some
pituitary adenomas grow slowly, enlarge by expansion and become demarcated from normal pituitary (macroadenomas have a diameter greater than 1 cm). They may be clinically silent or secrete
anterior pituitary hormones in excess such as
prolactin,
growth hormone (GH), or
adrenocorticotropic hormone (
ACTH) causing diseases like
prolactinoma,
acromegaly,
Cushing's disease or rarely
thyroid-stimulating hormone (TSH) or
gonadotropins (LH, FSH). The incidence of the various subtypes of
pituitary adenoma varies but the most common is
prolactinoma. Clinically non-functioning
pituitary adenomas (NFPAs), which do not secrete
hormones often cause local mass symptoms and represent one-third of
pituitary adenomas. Given the high prevalence of
pituitary adenomas and their heterogeneity (different
tumor subtypes), it is critical that clinicians have a thorough understanding of the potential abnormalities in pituitary function and prognostic factors for behavior of
pituitary adenomas in order to timely implement specific treatment modalities. Regarding pathogenesis of these
tumors genetics, epigenetics and signaling pathways are the focus of current research yet our understanding of pituitary
tumorigenesis remains incomplete. Although several genes and signaling pathways have been identified as important factors in the development of
pituitary tumors, current treatment modalities fail to completely control the disease and prevent the associated morbidity and mortality. This article reviews the advances in our understanding of
pituitary adenoma, the guidance in evaluation and management of different subtypes of
pituitary adenomas and the possibility of new therapeutic approaches.