Triiodothyronine treatment maintains surfactant synthesis during sepsis

Pulmonary compromise with altered surfactant metabolism is frequently noted during sepsis; triiodothyronine is necessary for normal surfactant synthesis. We evaluated the role of physiologic replacement of triiodothyronine during sepsis-induced hypothyroidism on surfactant synthesis and lung structural integrity.

Male Sprague Dawley rats (average weight, 330 gm) underwent sham laparotomy or cecal ligation and puncture; treatment was administered to rats that underwent cecal ligation and puncture by Alzet osmotic pump consisting of triiodothyronine (3 ng/hr) or saline control. The rats were killed 24 hours after serum triiodothyronine determination by radioimmunoassay (normal, 60 to 160 ng/dl). Surfactant was obtained by saline lavage. Lipid content was determined by Folch extraction; phospholipid content was verified by chromatography. Blinded histologic analysis of lung confluence and alveolar sparing was done in separate subgroups. Results are +/- SE.

Control rats with sepsis were hypothyroid at 24 hours; rats given triiodothyronine were euthyroid (rats that underwent sham laparotomy, 67.7 +/- 4.9 ng/dl; control rats, 37.6 +/- 5.7 ng/dl; and triiodothyronine, 85.7 +/- 19 ng/dl; p less than 0.05 compared with triiodothyronine by analysis of variance). Surfactant production was significantly improved by triiodothyronine compared with control (60.7 +/- 22.6 mg vs 23.2 +/- 11.3 mg; p less than 0.05 by analysis of variance). Lung histologic integrity was maintained by triiodothyronine treatment during sepsis.

Triiodothyronine supplementation may be beneficial in septic-induced pulmonary dysfunction.