What Is a Pituitary Adenoma and Why Does It Matter?
Pituitary adenomas are tumours that develop from the cells of the pituitary gland, almost all benign, and are classified along two main lines. The first is whether they secrete hormones: 'functional' adenomas produce excess hormone and create a disease picture — prolactinoma (milk discharge, menstrual irregularity, sexual dysfunction), a growth-hormone-secreting adenoma (enlargement of the hands, feet and facial features, acromegaly), a cortisol-secreting adenoma (Cushing's disease). 'Non-functional' adenomas do not produce hormone but cause compression symptoms as they grow. The second is size: those under 1 cm are called microadenomas, those above macroadenomas. The most important compression symptom is loss of visual field (typically narrowing from the sides) caused by pressure on the crossing point of the optic nerves (optic chiasm). For this reason both pituitary-protocol MRI and detailed hormone blood tests and an eye/visual-field examination are essential in diagnosis.
A Tumour Treatable with Medication: Prolactinoma
Among pituitary adenomas, prolactinoma holds a special place because it is the one pituitary tumour that mostly does not require surgery. These prolactin-secreting tumours usually respond very well to drugs called dopamine agonists (cabergoline, bromocriptine): the drug both returns the hormone level to normal and shrinks the tumour — indeed, even in large prolactinomas causing visual loss, the first choice is often medication. This illustrates an important rule of pituitary surgery: first the correct diagnosis, then the correct treatment. When a large pituitary tumour causing visual loss is seen, it is wrong to think automatically of surgery; if that tumour is a prolactinoma, medication is often more effective and safer than surgery. For this reason a hormone profile is always obtained before any operation for a pituitary tumour. In prolactinoma surgery is reserved for selected cases that do not respond to or cannot tolerate medication, or that have sudden visual loss.
Endoscopic Transsphenoidal Surgery
Surgery comes into play in hormone-secreting adenomas not treatable with medication (those secreting growth hormone or cortisol), in non-functional macroadenomas causing visual loss, and in drug-resistant prolactinomas. The standard of modern pituitary surgery is the endoscopic transsphenoidal approach: the skull is not opened; the tumour is reached through the nostrils, via the sphenoid sinus, under endoscopic guidance. This method is far less invasive than open surgery, leaves no external incision scar and has a shorter recovery. Often performed by a neurosurgeon and an ENT surgeon working together, this operation is carried out with neuronavigation. The aim is to relieve hormone excess in secreting tumours and to decompress the optic nerve in compressive tumours. The procedure usually takes 2–4 hours; a hospital stay of 2–4 days is usual afterwards. Hormone levels and urine balance are closely monitored after surgery.
Hormone Balance and Postoperative Follow-up
The most important point distinguishing pituitary surgery from other brain operations is that hormonal control is as critical as the surgery itself. Before surgery all pituitary hormones (cortisol, thyroid, growth hormone, prolactin, sex hormones) are evaluated together with an endocrinologist; any deficiency is corrected before surgery, and cortisol support in particular is important for safety. After surgery a temporary increase in urine output (diabetes insipidus) may be seen; this is mostly temporary and is monitored. In some patients pituitary function may decline partly or fully, requiring lifelong hormone-replacement therapy; this is discussed honestly before surgery. The success of treatment is measured not only by removal of the tumour but by preservation of hormone balance and recovery of vision. For this reason patients with pituitary tumours require a team approach in which neurosurgery, endocrinology and ophthalmology follow them together.
Risks and Realistic Expectations
Endoscopic transsphenoidal surgery is a safe method in experienced hands, but it is not without risk and these must be discussed honestly: cerebrospinal fluid (CSF) leak, temporary or permanent hormone deficiency, temporary urine imbalance (diabetes insipidus), rarely involvement of the visual or vascular structures, and general surgical risks. Outcomes vary with the type and size of the tumour: in small, hormone-secreting adenomas the chance of returning the hormone level to normal is high; some large tumours cannot be fully removed in a single operation and may require complementary medication or radiosurgery. Recently begun visual loss due to compression often improves with early surgery, but long-standing loss may not fully reverse. In no case is it guaranteed that 'the tumour will be completely removed' or that 'all hormones will return to normal'; expectations are shared openly with the patient after the tumour type, size and hormone profile have been assessed.