Abstract
A 44-yr-old man was admitted to Kagoshima University Hospital in April, 1975, due to episodes of unconsciousness and irrational behavior in the early morning. A chest X-ray taken 15 years previously showed an abnormal round shadow at the middle base of the left lung. However, the patient had been active and well until 4 months prior to his admission when he experienced his first episode.
A chest X-ray on admission revealed a huge intrathoracic tumor, which occupied most of the space of the left thoracic cage. After admission, he developed frequent episodes of hypoglycemia. His blood sugar levels at the time of the attacks were below 50 mg/d/, reaching 15 mg/d/ at minimum, and his levels of serum IRI were also low (3-10μU/m/). Suppressed secretion of endogenous glucagon was also observed. Tolbutamide and leucine exerted no apparent effect on IRI release. Celiac arteriography revealed no abnormal findings. Based on these results, insulinoma was ruled out. Pituitary and adrenocortical functions were normal, as was liver function. The possibility of hypoglycemia resulting from the presence of the huge intrathoracic tumor was thus indicated. In June, 1975, extirpation of the tumor was successfully carried out, and was followed by a complete disappearance of the hypoglycemic attacks.
The tumor originated in the left interlobular pleura, weighed 3, 020 g, was lobulated and encapsulated with a smooth surface. Histological examination revealed fibrosarcoma of low grade malignancy. The contents of glycogen, lactate and IRI in the tumor tissue were not elevated. The levels of ILA in acid-ethanol extracts of the tumor tissue and serum were so low as to be virtually undetectable. The activities of glycolytic enzymes, especially those of the key enzymes, hexokinase and pyruvate kinase, were higher in the tumor tissue than in normalred blood cells.
Over-consumption of blood glucose by the tumor tissue thus appears to represent one of the most probable mechanisms of the hypoglycemia observed in the present case. However, there is no definite evidence to show that such over-consumption resulted from high activities of glycolytic enzymes in the tumor tissue. The suppressed secretion of endogenous glucagon also appears to be one of the possible contributory factors to the hypoglycemic attacks.
