Endocrine manifestations of malignancy

Endocrine manifestations of cancer are primarily observed as paraneoplastic syndromes. These are rare systemic manifestations of malignancy due to non-size-related effects of the underlying cancer. The pathobiology of these syndromes is due to underlying production of hormones and related substances that act in an endocrine or paracrine manner on effector cells distributed through the body, thereby resulting in systemic manifestations. Two major mechanisms are observed: ectopic hormone production by tumours not involving endocrine organs, and malignancy of endocrine glands resulting in direct secretion of hormones. The most common paraneoplastic syndromes observed are hypercalcaemia of malignancy, Cushing's syndrome and the syndrome of inappropriate antidiuretic hormone, each of which may be the primary presenting feature of the underlying malignancy. Rarer syndromes result from ectopic production of less frequently observed bioactive proteins, e.g. growth hormone releasing hormone, human chorionic gonadotrophin, insulin-like growth factors, renin and vasoactive intestinal peptide. In this article we overview the spectrum of common and rare paraneoplastic syndromes observed and their manifestations.