Paraneoplastic hormonal syndromes

We can define paraneoplastic syndromes as a combination of effects occurring far from the original location of the tumour and independently from the local repercussion of its metastases. Paraneoplastic hormonal syndromes depend on the secretion of hormonal peptides or their precursors, cytokines and, more rarely, thyroidal hormones and Vitamin D, which act in an endocrine, paracrine or autocrine way. Sometimes, paraneoplastic syndromes can be more serious than the consequences of the primary tumour itself and can precede, develop in parallel, or follow the manifestations of this tumour. It is important to recognise a paraneoplastic hormonal syndrome for several reasons, amongst which we would draw attention to three: 1) It can lead to the diagnosis of a previously undetected, underlying malign or benign neoplasia; 2) It can dominate the clinical picture and thus lead to errors with respect to the origin and type of primary tumour; and 3) It can follow the clinical course of the underlying tumour and thus be useful for monitoring its evolution. The molecular mechanisms responsible for the development of these syndromes are not well-known, but it is believed that they might be inherent to the mutations responsible for the primary tumour or depend on epigenetic factors such as methylation. In this review, we consider the following paraneoplastic hormonal syndromes: malign hypercalcaemia, hyponatraemia (inappropiate secretion of the antidiuretic hormone), ectopic Cushing's syndrome, ectopic acromegaly, hypoglycaemia due to tumours different from those of the islet cells and paraneoplastic gynaecomastia; we make a brief final reference to other hormones (calcitonin, somatostatin, and VIP).