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.