ABSTRACT
ABSTRACT The pituitary gland is responsible for the synthesis and secretion of various hormones that play a key role in regulating endocrine function and homeostasis. Pituitary adenomas (PA) are benign epithelial tumors arising from the endocrine cells of the anterior pituitary gland. Clinically relevant PA are relatively common and they occur in 0.1% of the general population. They are mostly benign monoclonal neoplasms that arise from any of the five hormone-secreting cell types of the anterior pituitary gland. PA are categorized as either functioning or non-functioning, depending on whether or not they produce a hormonal hypersecretion syndrome. Both functioning and non-functioning adenomas can produce symptoms or signs resulting from compression of the optic chiasm or invasion of cavernous sinuses. Only 5% of PA occur within the context of hereditary syndromes with reasonably well-defined oncogenic mechanisms. The vast majority of PA are sporadic, and their etiopathogenesis remains largely unknown. Pituitary tumor oncogenesis involves several mechanisms that eventually lead to abnormal cell proliferation and dysregulated hormone production. Among these factors, we found inactivating mutations of tumor suppressor genes, activating mutation of oncogenes and the participation of hormonal signals coming from the hypothalamus, all resulting in cell-cycle regulation abnormalities. In this review, we summarize the clinical and pathophysiological aspects of the different hereditary pituitary tumor syndromes.