Pathophysiology of hypoalbuminemia associated with carcinoid tumor.

Decreased serum albumin levels are commonly observed in patients with carcinoid tumor, who also show several characteristic clinical and biochemical abnormalities. A large comparative study on a group of 96 carcinoid patients was performed with the purpose of identifying some of the mechanisms leading to hypoalbuminemia in patients with this form of cancer, and thereby to shed light on the cause of hypoalbuminemia of cancer in general. Serum albumin values were compared with a number of clinical parameters (including extent of liver metastases, severity of diarrhea, degree of right heart failure, and extent of gastrointestinal surgery) and of laboratory data (prothrombin time, BSP retention, serum transferrin concentration, hematocrit value, and daily urine excretion of 5-hydroxy-indoleacetic acid). In several patients the gastrointestinal protein loss was assessed by the 51Cr-albumin technique, whereas albumin renewal and distribution were evaluated by the use of 125I-albumin. The data obtained showed that the main factors in determining decreased serum albumin levels in patients with carcinoids are both reduced synthesis and increased loss of the protein. The hepatic synthetic defect appears to be related to a progressive decrease in the number of functioning liver cells; the origin of the gastrointestinal protein loss may be related to the obvious tumor involvement of the gut wall, as well as to the pharmacologically-induced diarrhea. Right heart failure occurring as a result of the carcinoid heart disease may be an additional cause for gastrointestinal protein loss in patients with carcinoid tumor.