Hypopituitarism and Non-Functioning Pituitary Adenomas
Non-functioning pituitary adenomas
Non-functioning pituitary adenomas (NFPAs) are bioc cally inert tumours. They usually present with the physical effects of a pituitary mass lesion (e.g. visual field loss, headache and hypopituitarism) or, increasingly, when discovered incidentally on routine brain MRI (‘pituitary incidentalomas’). Surgical decompression is indicated if there is a visual field defect or if the lesion is close to the optic chiasm.
The usual route for removal is trans-sphenoidally, although trans-cranial surgery is occasionally needed. NFPAs can cause hypopituitarism by compressing the normal gland, which requires endocrine replacement. Histologically, NFPAs can have positive immunostaining for inactive LH and FSH, but they do not secret bioactive hormones. Patients with significant postoperative residual tumour may require radiotherapy.
Hypopituitarism has several causes, either congenital (from pituitary transcription factor defects) or acquired. Acquired hypopituitarism is most commonly caused by the presence of a pituitary tumour. Other acquired causes include inflammatory and infiltratitive disorders, traumatic brain injury and radiotherapy (Figure 5.1). In patients with hypopituitarism and a large empty pituitary fossa on MRI, it is important to enquire about a previous history of severe headache, as this may reflect missed pituitary apoplexy (Chapter 36).