Hormone Secretion in Pituitary Adenomas: Immunohistochemical Studies

Classification of pituitary adenomas is still changing and not completely satisfying. Various types of hormones, prehormonal substances, and transcription factors are detected in pituitary adenomas. Monohormonal secretion in pituitary adenomas is frequent, notably prolactin secretion. Secretion of more than one hormone normally originating from the same adenohypophyseal cell lineage is well known, classically GH-PRL and FSH-LH. Other combinations of hormonal secretion are reported; they are sometimes underestimated. Plurihormonal secretion in pituitary adenomas, which is secretion of hormones that are normally originating from different adenohypophyseal cell lineages, is usually underestimated and in most cases remains subclinical. An immunohistochemical study of all pituitary hormones and prehormonal substances, as demonstrating transcription factors, is not always available; it is frequently not performed. This chapter aims to show the underestimated and vague areas of pituitary adenomas and to emphasize the importance of immunohistochemical studies in the diagnosis and prediction of clinical outcomes of these adenomas.