J Endocrinol Metab

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

Journal website https://jem.elmerpub.com

Original Article

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

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

**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 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 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.

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
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 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

0.401 (χ² = 1.377; df = 1)

Decreased

Total

BW change

Increased

1.00 (χ² = 0.418; df = 1)

0.237 (χ² = 3.309; df = 1)

Decreased

Total

Group A and B

0.714 (χ² = 0.331; df = 1)

0.689 (χ² = 0.549; df = 1)

Total

BMI change

Increased

1.00 (χ² = 0.86; df = 1)

0.052 (χ² = 6.802; df = 1)

Decreased

Total

**Table 4.** Correlation Analysis Between Changes in TSH and fT4 Levels and Clinical Parameters
Variables	TSH change	fT4 change
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

Table 4. Correlation Analysis Between Changes in TSH and fT4 Levels and Clinical Parameters

Variables

TSH change

fT4 change

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