The pituitary – a small but mighty pea

The pituitary gland is a pea-sized (about 1 cm) structure that sits within the sella turcica (“Turkish saddle”), a cup-shaped depression in the sphenoid bone at the skull base. It is located behind the bridge of the nose, underneath the brain and optic chiasm.

Despite its small size, the pituitary gland the master regulator of the human *endocrine system, producing hormones also known as chemical messengers, that are released directly into the bloodstream. These hormones control and regulate metabolism, growth, reproduction, water balance and blood pressure. Hormone levels can be measured through blood and/ or urine tests.

*endocrine system is a messenger system comprising feedback loops of hormones released by glands directly into the circulatory system, regulating distant target organs
An increase or decrease in the particular hormone levels will result in physiological imbalance which could manifest clinically e.g giant statue, if there is significant increase in growth hormones. Excess of a particular hormone is generally due to presence of a pituitary growth/ tumour which could be cancerous or non-cancerous. Apart from hormonal imbalance, a growth in the pituitary can also affect its nearby structures such as the optic chiasm, causing visual field deficits and headache. If the pituitary tumour encroaches onto the nearby cavernous sinus, it can cause impairment of eye movements from cranial nerve palsy.

Types of pituitary tumours

Pituitary adenomas are the most common growths in the sella and parasellar region. They are slow-growing benign tumours arising from the anterior pituitary tissue. In medical imaging, they are classified by size, growths < 1 cm are termed micro-adenomas and those > 1 cm are macro-adenomas. On the other hand, the clinical classification separates adenomas that are functioning meaning those that are hormonally active and non-functioning meaning those that do not have measurable evidence of hormonal activity. Whether the tumours are hormonally active or not, the imaging appearance on MRI is the same.

The commonest functioning, non-cancerous pituitary growth/ tumour is prolactinoma (PRL). This is followed by somatotrophinoma (growth hormone). Corticotropinoma is uncommon and secretes adrenocorticotropic hormone (ACTH) derivatives, resulting in Cushing syndrome.

Apart from benign tumours, there are also malignant tumours of the pituitary but these are rare, accounting for only < 0.5% of all pituitary tumours. Most of these malignant tumours are functional, exhibiting effects of increased prolactin or ACTH.


MRI is the gold standard for the evaluation of the pituitary and its adjacent structures due to its excellent soft tissue resolution. Images obtained are before and after injection of dye, which has and continues to be the mainstay of pituitary imaging.


Depending on the size and nature of the pituitary tumour, the mode of management will be medical, surgical and/ or radiotherapy.

1. Shih RY, Schroeder JW and Koeller KK. Primary Tumors of the Pituitary Gland: Radiologic-Pathologic Correlation. Radiographics. Oct 1 2021.

2. Du Four S, Van Der Veken J, Duerinck J, Vermeulen E, Andreescu CE, Bruneau M, Neyns B, Velthoven V and Velkeniers B (2022) Pituitary carcinoma – case series and review of the literature. Front. Endocrinol. 13:968692. doi: 10.3389/fendo.2022.968692

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