Elevation of thyrotropin upon accidental hypothermia in an elderly man

Although "polar triiodothyronine (T(3)) syndrome" in chronic dwellers/workers in Antarctica has been established, alteration of the pituitary thyroid-axis upon accidental hypothermia is not well recognized. We report here a rare case of elevation of thyrotropin (TSH) upon accidental hypothermia.

A 75-year-old man was admitted because of consciousness disturbance.The mean outside temperature was approximately -2.0°C (28.4°F) but his house was inadequately heated. His rectal temperature was 29.5°C (85.1°F). Goiter was not palpable and pitting edema, not myxedema, was present. Serum TSH was elevated (28.3 mU/L, reference range 0.27-4.2), and free T(3) (FT(3)) and free thyroxine (FT(4)) lowered (FT(3), 3.25 pmol/L with a reference range of 4.00-7.85, and FT(4), 9.18 pmol/L with a reference range of 12.87-23.179), but thyroid-related autoantibodies were all negative. By the next morning, body temperature had risen to >36°C (>96.8°F) and there was no further recurrence of hypothermia. Serum TSH decreased exponentially and the patient's condition had become normal by day 22. FT(3) and FT(4) were found to be slightly lowered and elevated, respectively, during the same period, in the subnormal range. At the end of the observation period, the patient settled into the state known as "nonthyroidal illness syndrome."

Elevation of TSH in an elderly patient with accidental hypothermia was normalized after restoration of normal body temperature. Elevation of TSH upon accidental hypothermia was probably an adaptive response.

In patients with accidental hypothermia, the possibility of an adaptive elevation of TSH should be borne in mind. This clearly warrants further studies of the adaptation of the pituitary-thyroid axis in patients with accidental hypothermia.