 Administering TRH to patients with chronic illness, however, seems to normalize thyroid levels and improve catabolic function, although whether this is beneficial is unclear.When NTIS is caused by the normal fasting response to illness, early parenteral nutrition has been shown to attenuate alterations in thyroid hormone (TSH, T3, T4, rT3) levels, whereas late parenteral nutrition exacerbates it.However, late parenteral nutrition also reduced complications and accelerated recovery in one study.