Summary

• Clinically non-functional pituitary adenomas (CNFAs) are considered here; functional pituitary adenomas (e.g., acromegaly, Cushing's syndrome, prolactinoma) are dealt with separately.
• Small pituitary tumours (<4 mm) are common and have been reported in up to 10% of MRIs in the general population, with no clinical features suggestive of pituitary disorder.
• Radiologically, CNFAs are classified as micro-adenomas (<1 cm diameter) or macro-adenomas (≥1 cm diameter); they may have suprasellar extension towards the optic chiasm, lateral extension into the cavernous sinuses, or downward extension into the sphenoid.
• Patients with non-functional pituitary micro-adenomas require limited follow-up, but pituitary macro-adenomas need to be followed for life.
• Non-functional pituitary macro-adenomas typically come to medical attention with features of mass effect such as headaches, visual field deficits, hypopituitarism, and rarely cranial nerve palsies.
• A modest elevation of prolactin may occur in CNFAs due to compression of the pituitary stalk and interruption of intrinsic dopaminergic tone.
• Trans-sphenoidal surgery is the first-line therapy for patients with CNFAs and mass effect.