Journal of Endocrinology and Metabolism, ISSN 1923-2861 print, 1923-287X online, Open Access
Article copyright, the authors; Journal compilation copyright, J Endocrinol Metab and Elmer Press Inc
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Original Article

Volume 16, Number 1, February 2026, pages 15-21

Association Between Tirzepatide Therapy and Thyroid Function in Euthyroid Patients With Obesity

Tables

↓  Table 1. Baseline Demographic, Body Measurements, and Laboratory Characteristics of the Study Population and Comparison of Body Measurements and Thyroid Parameters According to Weight Loss Category (< 5% vs. > 5%)
 
Variables Total (n = 38) Group A: < 5% weight loss (n = 13) Group B: ≥ 5% weight loss (n = 25) P value
Variables with normal distribution were expressed as mean ± standard deviation (SD), while non-normally distributed variables were presented as median (minimum–maximum). F: female; M: male; BW: body weight; BMI: body mass index; HbA1c: glycated hemoglobin; LDL: low-density lipoprotein; HDL: high-density lipoprotein; TSH: thyroid-stimulating hormone; fT4: free thyroxine.
Age 38.03 ± 10.83 40.5 ± 12.5 36.7 ± 9.9 0.770
Sex (F/M) 28/10 11/2 17/8 0.263
Height (cm) 166.29 ± 9.524 165.2 ± 8.2 167.1 ± 9.9 0.563
Baseline BW (kg) 100.69 ± 16.94 98.76 ± 15.88 101.69 ± 17.7 0.701
Final BW (kg) 94.94 ± 16.39 96.4 ± 15.69 94.18 ± 17.02 0.622
Baseline BMI (kg/m2) 36.31 ± 4.74 36.46 ± 5.32 36.23 ± 4.52 0.939
Final BMI (kg/m2) 34.31 ± 4.69 35.75 ± 5.07 33.56 ± 4.41 0.224
Baseline fasting blood glucose (mg/dL) 91.92 ± 10.17 91.85 ± 12.38 91.96 ± 9.1 0.689
Final fasting blood glucose (mg/dL) 84.92 ± 8.21 84.77 ± 6.3 85 ± 9.16 0.890
Baseline HbA1c (%) 5.65 (3.7–6.4) 5.7 (4.1–6.4) 5.6 (3.7–6.4) 0.877
Final HbA1c (%) 5.5 (3.6–6.3) 5.5 (4.8–6.3) 5.5 (3.6–6) 0.101
Baseline TSH (µIU/mL) 2.66 ± 1.45 2.34 ± 1.36 2.82 ± 1.49 0.202
Final TSH (µIU/mL) 2.12 ± 1.28 1.79 ± 0.93 2.29 ± 1.41 0.196
Baseline fT4 (ng/dL) 0.75 ± 0.11 0.75 ± 0.08 0.76 ± 0.13 0.782
Final fT4 (ng/dL) 0.86 ± 0.10 0.84 ± 0.09 0.87 ± 0.11 0.356
Baseline LDL (mg/dL) 129.26 ± 29.39 132.23 ± 36.67 127.72 ± 25.53 0.538
Final LDL (mg/dL) 112.13 ± 22.77 116 ± 20.82 110.12 ± 23.87 0.288
Baseline HDL (mg/dL) 44.74 ± 8.53 46.15 ± 7.25 44 ± 9.17 0.304
Final HDL (mg/dL) 43.18 ± 9.11 47.77 ± 10.1 40.80 ± 7.71 0.228
Baseline triglycerides (mg/dL) 141 (71–462) 131 (71–288) 147 (78–462) 0.356
Final triglycerides (mg/dL) 117 (65–268) 114 (72–235) 120 (65–268) 0.770
Baseline total cholesterol (mg/dL) 208.77 ± 35.43 209.74 ± 45.68 208.26 ± 29.86 0.590
Final total cholesterol (mg/dL) 183.32 ± 30.88 190.88 ± 32.07 179.39 ± 30.15 0.242

 

↓  Table 2. Changes in Body Measurements, Glycemic Markers, Lipid Profile, and Thyroid Function Parameters Before and After 1 Month of Treatment
 
Variables Baseline Final P value Change Change, increased/decreased ES (Cohen’s d) 95% CI of ES Interpretation
Variables with normal distribution were expressed as mean ± standard deviation (SD), while non-normally distributed variables were presented as median (minimum–maximum). BW: body weight; BMI: body mass index; CI: confidence interval; ES: effect size; HbA1c: glycated hemoglobin; LDL: low-density lipoprotein; HDL: high-density lipoprotein; TSH: thyroid-stimulating hormone; fT4: free thyroxine.
BW 100.69 ± 16.94 94.94 ± 16.39 < 0.001 –5.75 ± 3.11 1/37 –1.85 –2.18, –1.52 Large
BMI 36.90 ± 4.91 35.21 ± 4.64 < 0.001 –1.69 ± 1.18 2/36 –1.69 –2.01, –1.37 Large
Fasting blood glucose 91.92 ± 10.17 84.92 ± 8.21 < 0.001 –7 ± 9.69 6/32 –0.72 –1.05, –0.39 Medium
HbA1c (%) 5.65 (3.7–6.4) 5.5 (3.6–6.3) 0.1 –0.10 (–0.70 to 0.70) 14/24 –0.25 –0.55, 0.05 Small
LDL 129.26 ± 29.39 112.13 ± 22.77 < 0.001 –17.13 ± 24.94 7/31 –0.69 –0.98, –0.40 Medium
HDL 44.74 ± 8.53 43.18 ± 9.11 0.185 –1.56 ± 7.09 19/19 –0.22 –0.50, 0.06 Small
Triglycerides 141 (71–462) 117 (65–268) 0.001 –31 (–230 to 96) 10/28 –0.55 –0.85, –0.25 Medium
Total cholesterol 208.77 ± 35.43 183.32 ± 30.88 < 0.001 –25.45 ± 33.62 5/33 –0.76 –1.06, –0.46 Medium
TSH 2.66 ± 1.45 2.12 ± 1.28 0.001 –0.54 ± 0.88 11/27 –0.61 –0.91, –0.31 Medium
fT4 0.75 ± 0.11 0.86 ± 0.10 < 0.001 0.11 ± 0.13 29/9 0.77 0.46, 1.08 Medium

 

↓  Table 3. Cross-Tabulation of Changes in TSH Levels According to Changes in fT4, BW, Percent Weight, and BMI
 
TSH change fT4 change
Increased Decreased Total P value Increased Decreased Total P value
Group A: < 5% weight loss; group B: ≥ 5% weight loss. BW: body weight; BMI: body mass index; TSH: thyroid-stimulating hormone; fT4: free thyroxine.
fT4 change Increased 7 22 29 0.401 (χ2 = 1.377; df = 1) 7 4 11 0.401 (χ2 = 1.377; df = 1)
Decreased 4 5 9 22 5 27
Total 11 27 38 29 9 38
BW change Increased 0 1 1 1.00 (χ2 = 0.418; df = 1) 0 1 1 0.237 (χ2 = 3.309; df = 1)
Decreased 11 26 37 29 8 37
Total 11 27 38 29 9 38
Group A and B A 3 10 13 0.714 (χ2 = 0.331; df = 1) 9 4 13 0.689 (χ2 = 0.549; df = 1)
B 8 17 25 20 5 25
Total 11 27 38 29 9 38
BMI change Increased 0 2 2 1.00 (χ2 = 0.86; df = 1) 0 2 2 0.052 (χ2 = 6.802; df = 1)
Decreased 11 25 36 29 7 36
Total 11 27 38 29 9 38

 

↓  Table 4. Correlation Analysis Between Changes in TSH and fT4 Levels and Clinical Parameters
 
Variables TSH change fT4 change
r P value r P value
r denotes the correlation coefficient, indicating the strength and direction of the association. P value indicates the statistical significance of the correlation. BW: body weight; BMI: body mass index; TSH: thyroid-stimulating hormone; fT4: free thyroxine.
Baseline BW (kg) –0.020 0.904 0.099 0.553
Final BW (kg) –0.005 0.977 0.032 0.849
BW change –0.026 0.877 –0.327 0.045
Baseline BMI (kg/m2) –0.203 0.221 0.220 0.185
Final BMI (kg/m2) –0.172 0.302 0.114 0.496
BMI change 0.051 0.761 –0.358 0.027
Baseline TSH (µIU/mL) –0.571 < 0.001 0.270 0.101
Final TSH (µIU/mL) 0.188 0.257 0.160 0.337
Baseline fT4 (ng/dL) 0.003 0.987 –0.499 0.001
Final fT4 (ng/dL) –0.136 0.416 0.605 < 0.001