Thyroid hormones in conditions of chronic malnutrition. A study with special reference to cancer cachexia

Circulating levels of thyroid hormones (T4, free T4, T3) and reverse tri-iodo thyronine (rT3) and thyroid-hormone binding globulin were related to the nutritional state of patients with cancer cachexia, patients with malnutrition due to other reasons and to well-nourished patients with acute illness. Hospitalized weight-stable and well-nourished patients served as controls. Malnourished patients with or without cancer and acutely ill patients had a low T3 syndrome involving both peripheral metabolism of thyroid hormones and the hypothalamus-pituitary-thyroid gland axis. T3 levels were correlated to altered protein metabolism and protein nutritional state. There were pronounced elevations of circulating rT3 concentrations in patients with serum albumin concentration less than 35 g/l irrespective of diagnosis. The results indicate that the low T3 syndrome in our patients is secondary to insufficient caloric intake. It seems to be maintained by the abnormal nutritional state and is related closely to protein metabolism. The authors found no differences between the low T3 syndrome in cancer patients suffering from cachexia compared with that of patients with malnutrition caused by other factors.