[Nonthyroidal illness syndrome in acute bacterial endotoxicosis: pathogenesis and methods of correction].

Nonthyroidal illness syndrome is characterized by alterations of thyroid status inpatients with severe nonthyroidal illness who are clinically euthyroid. Mechanisms of nonthyroidal illness syndrome are poorly understood and controversial. Our investigations on nonthyroidal illness syndrome in acute endotoxicosis revealed two principal mechanisms of its development. The peripheral mechanism is the first to develop and referred to disturbance of thyrocytes secretory cycle due to increase of thyroglobulin synthesis, endocytosis and decrease of its proteolytic cleavage. It manifests with drop of serum thyroxine, not triiodthyronine, and increase of serum thyroid stimulating hormone. The central mechanism is associated with hypothalamic-pituitary hypofunction developed simultaneously with systemic inflammatory response. Rate of supplementation of the peripheral mechanism with the central one accounts for different types of nonthyroidal illness syndrome with high, normal and low serum levels of thyroid stimulating hormone. Our research showed that thyroid hormone replacement in nonthyroidal illness syndrome could only suppress thyroid function. Unlike thyroid hormones administration of thyroid stimulating hormone restores thyroid hormone secretion in nonthyroidal illness syndrome, decreases endotoxinemia and secretion of proinflammatory cytokines and improves liver function.