The pituitary gland lies in the pituitary fossa (sella turcica), which is situated in the middle cranial fossa at the base of the brain. It is linked functionally to the hypothalamus by the pituitary stalk. The hypothalamus lies in a superior position to the pituitary gland, and the link between the two organs is critical for normal pituitary gland function.
The anterior pituitary secretes growth hormone, thyrotropin or thyroid-stimulating hormone, corticotropin or adrenocorticotropic hormone, follicle-stimulating hormone, luteinizing hormone, and prolactin. The posterior lobe secretes arginine vasopressin (also called antidiuretic hormone) and oxytocin.
Pituitary masses may be classified based on their underlying etiology: for example, pituitary adenoma, pituitary hyperplasia, nonadenomatous tumors, and vascular, inflammatory, or infective lesions.
Most pituitary masses are caused by a pituitary adenoma; these are benign tumors arising from the anterior pituitary gland. Pituitary adenomas are classified as functional (hormone secreting) or nonfunctional, and can be further categorized by cell type or size, for example, microadenomas (<10 mm) or macroadenomas (>10 mm).[1]Arafah BM, Nasrallah MP. Pituitary tumors: pathophysiology, clinical manifestations and management. Endocr Relat Cancer. 2001 Dec;8(4):287-305.
http://erc.endocrinology-journals.org/content/8/4/287.long
http://www.ncbi.nlm.nih.gov/pubmed/11733226?tool=bestpractice.com
[2]Molitch ME. Diagnosis and treatment of pituitary adenomas: a review. JAMA. 2017;317:516-524.
http://www.ncbi.nlm.nih.gov/pubmed/28170483?tool=bestpractice.com
[3]Pal A, Leaver L, Wass J. Pituitary adenomas. BMJ. 2019 Jun 6;365:l2091.
https://www.bmj.com/content/365/bmj.l2091.long
http://www.ncbi.nlm.nih.gov/pubmed/31171544?tool=bestpractice.com
[4]Nishioka H, Inoshita N. New WHO classification of pituitary adenomas (4th edition): assessment of pituitary transcription factors and the prognostic histological factors. Brain Tumor Pathol. 2018 Jan 9;35(2):57-61.
http://www.ncbi.nlm.nih.gov/pubmed/29318396?tool=bestpractice.com
Pituitary masses may present with a clinical syndrome resulting from hypersecretion of ≥1 anterior pituitary hormones (e.g., Cushing disease, acromegaly). Alternatively, they may present more insidiously with mass effect or with tumor expansion leading to compression of surrounding structures, including normal pituitary tissue, resulting in hypopituitarism. Functional pituitary tumors can produce a complex picture of combined hormonal excess and/or deficiencies.[1]Arafah BM, Nasrallah MP. Pituitary tumors: pathophysiology, clinical manifestations and management. Endocr Relat Cancer. 2001 Dec;8(4):287-305.
http://erc.endocrinology-journals.org/content/8/4/287.long
http://www.ncbi.nlm.nih.gov/pubmed/11733226?tool=bestpractice.com
Analyses using autopsy and radiologic data suggest primary adenoma prevalence rates of 14.4% and 22.5%, respectively (yielding an overall estimated prevalence rate of 16.7%).[5]Ezzat S, Asa SL, Couldwell WT, et al. The prevalence of pituitary adenomas: a systematic review. Cancer. 2004 Aug 1;101(3):613-9.
https://acsjournals.onlinelibrary.wiley.com/doi/full/10.1002/cncr.20412
http://www.ncbi.nlm.nih.gov/pubmed/15274075?tool=bestpractice.com
Almost all of these are clinically silent microadenomas. The prevalence increases with age, and detection is more likely using high-resolution MRI sequences.[6]Morris Z, Whiteley WN, Longstreth WT Jr, et al. Incidental findings on brain magnetic resonance imaging: systematic review and meta-analysis. BMJ. 2009;339:b3016.
http://www.bmj.com/content/339/bmj.b3016.full
http://www.ncbi.nlm.nih.gov/pubmed/19687093?tool=bestpractice.com
