Plasma leptin concentrations in relation to sick euthyroid syndrome in elderly patients with nonthyroidal illnesses

Background: Leptin, the ob gene product, seems to be involved in regulating energy expenditure in humans, but its role in the pathophysiology of the e nergy imbalance in chronically ill patients is largely unknown. Objective: To evaluate plasma leptin concentrations and thyroid function in elderly pa tients with nonthyroidal illnesses (NTl). Methods: Sixty-four NTI elderly p atients (75.0 +/- 6.3 years, 27 males and 37 females) and 21 age-and sex-ma tched healthy controls (73.0 +/- 5.5 years, 9 males and 12 females) were en rolled in the study. In all subjects tri-iodothyronine (T-3), thyroxine (T- 4), reverse T-3 (rT(3)), free T-3 (fT(3)), free T-4 (fT(4)), TSH, and plasm a leptin concentrations were measured. Nutritional status was also evaluate d in all subjects studied by the measurement of body mass index (BMI), lymp hocytes, serum iron, hemoglobin, plasma albumin, transferrin and total chol esterol. Results: The data on thyroid hormones enabled us to identify three groups: group A, subjects (15 patients) with T-3 and fT(3) levels comparab le to those of controls; group B, subjects (25 patients) with T-3 and fT(3) levels lower than controls and rT(3) levels comparable to those of control s; group C, subjects (24 patients) with Tg and fT(3) levels lower than thos e of controls and high rT(3) levels. The patients of group C showed lower p lasma leptin levels than the controls, 6.6 (5.5-14.2) and 16.3 (7.2-23.7) n g/ml (median with interquartile range in parentheses, p < 0.05), respective ly. Females also showed higher plasma leptin levels than males in the contr ols, group A and group B, but not in group C. Moreover, plasma leptin conce ntrations were directly correlated to BMI in all the groups studied, while a negative correlation between leptin and rT(3) was detectable in group C ( r = -0.44, p < 0.05), also after adjusting for BMI and sex. Conclusions: Th e concurrence of modifications in plasma leptin and thyroid hormones concen trations found in elderly NTI patients with a sick euthyroid syndrome could reflect a particular neuroendocrine status, leading to a reduction in the catabolic processes in the course of chronic diseases. Copyright (C) 2000 S .Karger AG, Basel.