Diagnosis of ectopic ADH syndrome is made on the basis of the criteria described in Fig. 21.11.
Differential Diagnosis of Ectopic ADH Syndrome
Under rare conditions, inappropriate ADH secretion from the posterior pituitary gland in cancer patients is observed. Certain drugs, including vinca alkaloids, cyclophosphamide, barbiturates and morphine, may cause SIADH by stimulating ADH secretion from the posterior pituitary. Metastatic tumours in the hypothalamus and inflammatory changes, as well as the tumour mass may present in the intrathoracic cavity, may stimulate the secretion of ADH from the posterior pituitary gland. Since these disorders are sometimes difficult to differentiate from ectopic ADH syndrome, the final diagnosis of this syndrome is made by demonstration that the neoplasm produces a large amount of ADH.
