Non-β-cell tumor hypoglycemia associated with increased nonsuppressible insulin-like protein (NSILP)

An elderly woman with a massive intra-abdominal fibrosarcoma was noted to have intermittent hypoglycemia. When present, the hypoglycemia was associated with diminished levels of free fatty acids and ketone bodies and an increase in plasma NSILP. Lesser elevations of NSILP were observed on two of three occasions when the patient was normoglycemic. Insulin, somatomedin-C and NSILA-s levels were always low. Plasma glucagon increased appropriately in response to hypoglycemia; however, on three occasions, the plasma glucose response to intravenously administered glucagon was blunted. Low levels of amino acids were detected at all times; the concentration of alanine, the major gluconeogenic amino acid, was particularly low and diminished still further during several fasts during which the patient became hypoglycemic. Exogenous alanine caused a modest increase in plasma glucose. Thus, hypoglycemia was associated with hypoalaninemia, inhibition of lipolysis and impaired responsiveness to glucagon. To our knowledge, this is the first report of tumor-induced hypoglycemia associated with increased plasma NSILP.