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. 2020 Jul 2;105(9):e3090–e3104. doi: 10.1210/clinem/dgaa430

Figure 1.

Figure 1.

A, Integrated mean 24-hour serum triiodothyronine (T3) and thyrotropin (TSH) profiles following the indicated L-triiodothyronine (LT3) doses and levothyroxine (LT4) therapy. LT4 doses varied between 100 and 150 μg/day. The 24-hour serum T3 profiles were similar after LT3 20 or 25 μg/day or LT4 100 to 150 μg/day but 24-hour serum thyrotropin profiles were significantly less on LT4 than either LT3 20 or 25 μg/day (P < .001). Furthermore, the 24-hour serum T3 profile on LT3 50 μg/day was significantly higher (P < .01) than on LT4, yet the 24-hour serum thyrotropin profile was significantly lower on LT4 than LT3 50 μg/day (P ~ .05). Statistics were performed by paired t test of the 24-hour integrated hormone values. B, On LT3 10 μg/day the serum cholesterol was significantly reduced (352 to 270 mg/dL; P < .05). After the LT3 dose was increased to 20 μg/day, mean basal metabolic rate (BMR) (–3%) and serum cholesterol (215 mg/dL) were significantly different from baseline values (P < .001). On LT3 25 and 50 μg/day, and after 6 weeks of LT4 therapy, mean BMR and serum cholesterol were similar to and not significantly different from those values obtained while on LT3 20 μg/day. However, switching from LT3 50 μg/day to LT4 resulted in a significant drop in BMR (P < .03). Reproduced from (68).