Clinically nonfunctioning pituitary tumours and gonadotropinomas

The significant progress that has been made in the past years in the medical treatment of all pituitary adenomas is in stark contrast with the lack of progress in the medical treatment of clinically nonfunctioning pituitary tumours, or adenomas. In fact, only secreting, or functioning, tumours can be treated by medical therapy with at least modest to very impressive effect. Clinically nonfunctioning pituitary adenomas do not produce clinical signs of hormonal hypersecretion. Therefore, signs and symptoms will depend on the mass effect of these adenomas over the central nervous system (1–3).

Due to the lack of hypersecretion of hormones, nonfunctioning pituitary adenomas present themselves because of their mass effect and compression or destruction of surrounding tissues. This could also lead to hypopituitarism, which can be the presenting symptom as well (1–3). Despite their histologically benign nature, giant and ‘invasive’ nonfunctioning pituitary adenomas are one of the most complex neurosurgical challenges. Large nonfunctioning pituitary tumours are usually confined inferiorly by the sellar dura, superiorly by the elevated sellar diaphragm, and laterally by an intact medial wall of the cavernous sinus. If the anatomical extensions of the tumour are understood and a radical tumour resection is achieved, the visual and long-term outcome can be very rewarding. The goals of surgery are twofold: first to make a pathological diagnosis, and second, because these tumours are endocrinologically silent, to decompress the neural tissue (4). The vast majority of nonfunctioning pituitary adenomas are gonadotroph cell adenomas, as demonstrated by immunocytochemistry. However, they are rarely associated with increased levels of dimeric luteinizing hormone or follicle-stimulating hormone. Increased levels of subunits (free α-subunit mainly, LH-B subunit more rarely), however, are more frequently encountered, but are generally modest (5).

In this chapter the term ‘clinically nonfunctioning pituitary adenomas’ is used to describe pituitary tumours, which in most instances produce low quantities of hormones causing no clinically recognizable symptomatology. In the few instances, in which such tumours produce intact gonadotropins that activate testicular or ovarian activity, the term ‘gonadotropinomas’ is used.