Bacterial lipopolysaccharide (LPS)-induced type 2 iodothyronine deiodinase (D2) activation in the mediobasal hypothalamus (MBH) is independent of the LPS-induced fall in serum thyroid hormone levels.

By administration of bacterial lipopolysaccharide (LPS) to intact and T4-replaced thyroidectomized rats, we demonstrate that in contrast to the cortex and anterior pituitary, there is a persistent increase in type 2 iodothyronine deiodinase (D2) activity in the mediobasal hypothalamus (MBH). We propose that endotoxin-induced D2 activation in the MBH is independent of circulating levels of thyroid hormone and that this mechanism may contribute to central hypothyroidism associated with infection.