Paraneoplastic Syndromes

SIADH:
Five to ten percent of patients have SIADH at the time of diagnosis. However, 60-70% of patients have sub-clinical abnormalities in renal excretion of free water. Thirty to forty percent of patients have abnormally high ADH levels in their blood sometime during their illness.
Cushings:
Three to seven percent of patients with small cell carcinoma show actual Cushing's Syndrome. Yet many more show sub-clinical evidence of ACTH production. Thirty to forty percent have increased serum ACTH. Fifty percent have increased midnight cortisol levels. In addition to ACTH, these tumors often produce fragments of ACTH.
Calcitonin:
Fifty-five to sixty-five percent of patients have been noted to have elevated calcitonin levels. This has shown no clinical significance.
Eaton-Lambert:
While a wide variety of neurologic syndromes have been associated with small cell carcinoma, the one most commonly associated is Eaton-Lambert Syndrome (myasthenic). In the Mayo Clinic Series, 70% of their patients had the syndrome at some time during their illness. Other lesions vary from encephalopathy to peripheral neuropathy.