[Practical value of new knowledge on the structure and function of pituitary adenomas]

The usual classification of pituitary adenomas into eosinophilic, basophilic, and chromophobe types is no longer sufficient to correlate the histologic findings with the increasing number of clinical syndromes described in recent years. Some histologic forms are observed in several clinical syndromes, whereas some clinical entities may be caused by several histologic types. A new classification is mandatory. Recent endocrine, ultrastructural and histo-immunologic research has shown that the endocrine inactive adenoma, which has usually been related to the "chromophobe" adenoma, represents only a small group of the pituitary neoplasms. A more critical evaluation shows that 3 out of 4 patients present clinical or endocrine signs and findings of increased hormone secretion. Several authors have therefore suggested that pituitary adenomas be classified according to their secretory characteristics, which can be determined either by clinical and endocrine examination or by immunohistology and electron microscopy. Abnormally increased hormone secretion allows early detection of the neoplasm when the remaining normal gland is still able to recover its normal function and the endocrine symptoms therefore are fully reversible. The therapy of pituitary adenomas must normalize the hormone hypersecretion without causing new endocrine deficits, and must at the same time reverse neurological compression symptoms. The treatment may be either surgical excision, irradiation, medical inhibition of abnormal secretion, substitution of insufficient hormones or a combination of these methods. The prognosis of the endocrine symptoms is significantly better in small adenomas and full restoration of sexual function is even observed in an increasing number of patients.