Assessment of pituitary mass

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, thyrotrophin or thyroid-stimulating hormone, corticotrophin or adrenocorticotrophic hormone, follicle-stimulating hormone, luteinising hormone, and prolactin. The posterior lobe secretes arginine vasopressin (also called antidiuretic hormone) and oxytocin.

Pituitary masses may be classified based on their underlying aetiology: for example, pituitary adenoma, pituitary hyperplasia, non-adenomatous tumours, and vascular, inflammatory, or infective lesions.

Most pituitary masses are caused by a pituitary adenoma; these are benign tumours arising from the anterior pituitary gland. Pituitary adenomas are classified as functional (hormone secreting) or non-functional, and can be further categorised by cell type or size, for example, microadenomas (<10 mm) or macroadenomas (>10 mm).​[1]Tritos NA, Miller KK. Diagnosis and management of pituitary adenomas: a review. JAMA. 2023 Apr 25;329(16):1386-98. http://www.ncbi.nlm.nih.gov/pubmed/37097352?tool=bestpractice.com ​​[2]Pal A, Leaver L, Wass J. Pituitary adenomas. BMJ. 2019 Jun 6;365:l2091. http://www.ncbi.nlm.nih.gov/pubmed/31171544?tool=bestpractice.com [3]Asa SL, Mete O, Perry A, et al. Overview of the 2022 WHO classification of pituitary tumors. Endocr Pathol. 2022 Mar;33(1):6-26. http://www.ncbi.nlm.nih.gov/pubmed/35291028?tool=bestpractice.com

Pituitary masses may present with a clinical syndrome resulting from hypersecretion of ≥1 anterior pituitary hormones (e.g., Cushing's disease, acromegaly). Alternatively, they may present more insidiously with mass effect or with tumour expansion leading to compression of surrounding structures, including normal pituitary tissue, resulting in hypopituitarism. Functional pituitary tumours can produce a complex picture of combined hormonal excess and/or deficiencies.[4]Arafah BM, Nasrallah MP. Pituitary tumors: pathophysiology, clinical manifestations and management. Endocr Relat Cancer. 2001 Dec;8(4):287-305. https://erc.bioscientifica.com/view/journals/erc/8/4/11733226.xml http://www.ncbi.nlm.nih.gov/pubmed/11733226?tool=bestpractice.com

Analyses using autopsy and radiological 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