Elevation of Plasma TSH During Surgical Hypothermia

Abstract

Plasma TSH determinations were performed in 7 infants, aged 1.5–13 months, during hypothermic cardiovascular surgery. Rectal temperatures reached a mean nadir of 18 C. Elevations in plasma TSH were found in 6 subjects. The rise in plasma TSH occurred prior to the attainment of maximal hypothermia in 5 subjects, and in 3 subjects maximal TSH concentrations corresponded in time to the lowest temperatures reached. No rises in plasma TSH, in contrast, were encountered in 6 infants during cardiac catheterization and in 6 infants undergoing nonhypothermic surgery. It is concluded that TSH secretion can be activated in human infants subjected to cold exposure. This response may represent a homeostatic adjustment to increased thermogenic need.