Abstract.
We used microcalorimetry to measure lymphocyte heat production rate in patients with clinical and laboratoy hyperthyroidism (serum TSH ↓, serum FT4 ↑, serum FT3 ↑ ), subclinical hyperthyroidism (serum TSH ↓, serum FT4 ↑, serum FT3=), and subclinical hypothyroidism (serum TSH ↑, serum FT4 ↓, serum FT3=) compared with healthy controls (N= 13). The lymphocyte heat production rate was significantly correlated to the free thyroxine level (r=0.53, p<0.01) and to the free triiodothyronine level (r=0.51, p<0.01) when calculated from pooled data for the three patients groups. The hyperthyroid patients (N = 8) had a significantly increased lymphocyte heat production rate, 3.43±0.25 pW/cell, as compared with 2.31±0.12 pW/cell in the control group (p<0.001). The groups with subclinical hyperthyroidism (N = 7) and subclinical hypothyroidism (N=9) had lymphocyte heat production rates of 2.14±0.11 and 2.56±0.15 pW/cell, respectively, not significantly different from that in the controls. Consistently, there was no significant difference between patients with subclinical hyperthyroidism (N=5) and controls (N=5) with regard to lymphocyte energy production as calculated from separately measured oxygen comsumption rates in vitro, 1.36±0.20 and 1.56±0.12 pW/cell, respectively. Thus microcalorimetry seems to be suitable for studying the influence of thyroid hormones on cellular metabolism. Subclinical thyroid dysfunction does not seem to alter the overall rate of lymphocyte metabolism.