POMC and inappropriate ADH syndrome: Moreover, due to the SCLC neuroendocrine (NE) nature, patients with this tumor may develop serious para-neoplastic syndromes, like Cushing syndrome (increased ACTH), the syndrome of inappropriate antidiuretic hormone (SIADH), and neuromuscular syndromes, such as Lambert-Eaton myasthenic syndrome (LEMS) (production of autoantibodies against voltage-gated calcium channels in the presynaptic neuronal cell membrane).