Pituitary Adenoma (Pituitary Tumour)

What is a Pituitary Adenoma?

A pituitary adenoma is a benign (non-cancerous) tumour arising from the pituitary gland — a small but critically important gland situated at the base of the brain in a bony pocket called the sella turcica. The pituitary is known as the 'master gland' because it controls the release of many important hormones that regulate growth, metabolism, reproduction, stress response, and fluid balance.

Pituitary adenomas are the most common tumours of the pituitary region, accounting for approximately 10–15% of all intracranial tumours. They are classified by size (microadenoma <10mm; macroadenoma ≥10mm) and by hormone production (functioning or secreting adenomas, which produce excess hormone; and non-functioning adenomas, which do not).

At One Brain and Spine, our neurosurgeons work closely with endocrinologists and ophthalmologists in a multidisciplinary pituitary team, ensuring comprehensive management of all pituitary adenomas in Melbourne.

What Causes Pituitary Adenomas?

Most pituitary adenomas occur sporadically without a known cause. A small proportion are associated with:

• Multiple Endocrine Neoplasia type 1 (MEN1) — a genetic syndrome predisposing to pituitary, parathyroid, and pancreatic tumours
• Carney complex — a rare genetic syndrome
• McCune-Albright syndrome
• Familial isolated pituitary adenoma (FIPA)

The vast majority of patients have no family history or genetic predisposition. Pituitary adenomas are not caused by diet, lifestyle, or environmental exposures.

 Symptoms of a Pituitary Adenoma

Pituitary adenomas cause symptoms through two main mechanisms: mass effect (the tumour pressing on adjacent structures) and hormonal disturbance (either excess hormone secretion or deficiency from gland compression).‍

Mass Effect Symptoms

• Headache — from pressure within the sella turcica
• Visual disturbance — compression of the optic chiasm (where the optic nerves cross above the pituitary) causes characteristic bitemporal visual field loss; urgently requires assessment
• Cranial nerve palsy — compression of nerves in the cavernous sinus causes diplopia (double vision) or facial numbness
• Hypopituitarism — compression of the normal pituitary gland impairs hormone production, causing fatigue, low libido, menstrual disturbance, or adrenal insufficiency

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Hormone Excess Syndromes (Functioning Adenomas)

• Prolactinoma — excess prolactin causes menstrual irregularity, infertility, and galactorrhoea (milk production) in women; and reduced libido and erectile dysfunction in men. The most common secreting pituitary adenoma.
• Acromegaly — excess growth hormone causes enlargement of hands, feet, and facial features; joint pain; diabetes; hypertension; and sleep apnoea. Caused by a GH-secreting adenoma.
• Cushing's disease — excess ACTH stimulates the adrenal glands to produce excess cortisol, causing weight gain (particularly central), facial rounding, stretch marks, easy bruising, hypertension, and diabetes. Caused by an ACTH-secreting adenoma.
• Hyperthyroidism — rare; caused by a TSH-secreting adenoma

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Apoplexy

• In 5% of cases a pituitary adenoma can bleed, resulting in a sudden increase in pressure in the pituitary region.  This can lead to sudden blindness, and a hormone crisis with complete loss of pituitary function.  This presentation is an emergency and will require immediate hormone replacement and ur

How is a Pituitary Adenoma Diagnosed?

• MRI of the pituitary with gadolinium contrast — the gold standard imaging investigation; identifies adenoma size, extension, and relationship to optic chiasm and cavernous sinuses; a dedicated pituitary protocol MRI provides optimal detail;  It is not uncommon for a pituitary adenoma to be diagnosed incidentally due to having an MRI brain for a separate reason.  Your neurosurgeon may ask you to have a second MRI which is specific to the pituitary as a follow-up scan.
• Hormonal blood tests — assess pituitary hormone levels (prolactin, GH, IGF-1, ACTH, cortisol, TSH, FSH, LH, testosterone/oestrogen) to identify secreting adenomas and hypopituitarism
• Formal visual field testing (perimetry) — mandatory when a macroadenoma is identified, to assess for chiasmal compression
• Inferior petrosal sinus sampling (IPSS) — in cases of suspected Cushing's disease, this specialised test helps confirm a pituitary source of excess ACTH

Treatment Options for Pituitary Adenomas

Treatment depends on the tumour type, size, hormonal status, and the presence of visual compromise or other symptoms. Management is coordinated within the multidisciplinary pituitary team.

Medical Therapy

Prolactinomas are typically treated with dopamine agonist medications (cabergoline or bromocriptine) as first-line therapy — these drugs normalise prolactin levels and shrink tumours in the majority of patients, often avoiding surgery. Medical therapy for GH-secreting adenomas (somatostatin analogues) and Cushing's disease (steroidogenesis inhibitors) may also be used, though surgery is the first line treatment for these conditions.

Observation

Small, non-functioning microadenomas without visual compromise or significant hormone excess may be safely observed with regular MRI and endocrine monitoring.  There are also some macroadenomas which can be safely monitored also and your neurosurgeon will discuss these options with you.

Surgery — Transsphenoidal Resection

Surgery is the primary treatment for most non-functioning macroadenomas, GH-secreting adenomas (acromegaly), ACTH-secreting adenomas (Cushing's disease), and prolactinomas not responding to medical therapy. Surgery will also be recommended for tumours that should evidence of continued growth on surveillance MRI scans.

The standard surgical approach is transsphenoidal — operating through the nose and sphenoid sinus to access the pituitary gland without an external incision or brain retraction. Modern endoscopic transsphenoidal surgery provides excellent visualisation and allows removal of most pituitary adenomas safely and effectively. One Brain and Spine's neurosurgeons perform endoscopic transsphenoidal surgery for pituitary tumours in Melbourne.

Radiotherapy / Stereotactic Radiosurgery

Radiotherapy or stereotactic radiosurgery (Gamma Knife) may be used for residual or recurrent adenomas following surgery, or for patients unsuitable for surgery.