Thyroid-stimulating hormone levels and suicide attempts in Chinese patients with first-episode drug-naïve major depressive disorder

Table 1 Sociodemographic and clinical features of the participants (n = 1718), mean ± SD/n (%)/median (tertile low-tertile high)

Thyroid-stimulating hormone index (μIU/mL) tertiles	Low (0.36-3.78)	Middle (3.78-6.05)	High (6.06-13.01)	P value	P value1
Number	571	574	573
Age (years)	33.91 ± 12.24	34.56 ± 12.42	36.14 ± 12.54	0.007	0.006
Duration of illness (months)	4.98 ± 3.85	7.11 ± 5.08	7.08 ± 4.71	< 0.001	< 0.001
Age at onset (years)	33.78 ± 12.20	34.31 ± 12.27	35.89 ± 12.38	0.010	0.008
Hamilton Depression Scale continuous	28.60 ± 2.61	30.26 ± 2.60	32.02 ± 2.56	< 0.001	< 0.001
Hamilton Anxiety Scale	19.98 ± 2.81	19.89 ± 3.32	22.53 ± 3.57	< 0.001	< 0.001
Anti-thyroglobulin (IU/L)	41.53 (88.54), 18.82 (8.43-1122.00)	85.46 (205.28), 20.05 (2.20-2104.00)	142.92 (339.60), 24.36 (3.23-4222.00)	< 0.001	< 0.001
Thyroid peroxidase antibody (IU/L)	35.22 (98.36), 15.51 (1.59-1419.00)	58.86 (120.46), 16.21 (2.60-929.41)	122.62 (228.56), 25.62 (4.67-1812.84)	< 0.001	< 0.001
Free triiodothyronine (pmol/L)	4.87 (0.68), 4.90 (3.10-6.80)	4.93 (0.76), 4.95 (1.60-7.10)	4.92 (0.72), 5.00 (3.10-6.80)	0.285	0.215
Free thyroxine (pmol/L)	16.79 (3.09), 16.60 (7.80-23.00)	16.52 (3.09), 16.32 (8.90-23.21)	16.80 (3.10), 16.58 (10.38-32.10)	0.240	0.262
Fasting blood glucose (mmol/L)	5.09 (0.56), 5.02 (3.98-7.33)	5.38 (0.52), 5.40 (4.01-7.72)	5.73 (0.68), 5.71 (3.71-8.20)	< 0.001	< 0.001
Total cholesterol (mmol/L)	4.64 (0.93), 4.60 (2.17-8.80)	5.03 (0.84), 5.03 (2.34-7.89)	6.09 (0.98), 6.18 (2.95-8.56)	< 0.001	< 0.001
High-density lipoprotein cholesterol (mmol/L)	1.31 (0.24), 1.28 (0.60-2.23)	1.30 (0.25), 1.28 (0.56-2.04)	1.05 (0.29), 0.99 (0.44-1.84)	< 0.001	< 0.001
Triglycerides (mmol/L)	2.05 (1.01), 1.80 (0.34-7.54)	2.11 (0.93), 1.89 (0.17-5.82)	2.35 (0.99), 2.24 (0.42-7.21)	< 0.001	< 0.001
Low-density lipoprotein cholesterol (mmol/L)	2.64 (0.73), 2.50 (1.00-5.80)	2.80 (0.75), 2.80 (0.80-5.50)	3.51 (0.83), 3.50 (1.10-6.00)	< 0.001	< 0.001
Body mass index (kg/m2)	23.84 (1.73), 23.68 (18.07-29.17)	24.65 (1.90), 24.46 (16.23-31.99)	24.61 (2.02), 24.53 (17.72-39.00)	< 0.001	< 0.001
Systolic pressure (mmHg)	113.47 (10.73), 113.00 (90.00-148.00)	118.85 (8.99), 120.00 (90.00-159.00)	126.11 (9.02), 126.00 (90.00-160.00)	< 0.001	< 0.001
Diastolic pressure (mmHg)	73.51 (6.58), 73.00 (56.00-96.00)	75.37 (5.95), 75.00 (60.00-106.00)	78.96 (6.52), 78.00 (60.00-96.00)	< 0.001	< 0.001
Gender				0.998	-
Male	195 (34.15)	197 (34.32)	196 (34.21)
Female	376 (65.85)	377 (65.68)	377 (65.79)
Education				0.112	-
Junior high school	115 (20.14)	145 (25.26)	153 (26.70)
Senior high school	264 (46.23)	256 (44.60)	240 (41.88)
College	162 (28.37)	145 (25.26)	142 (24.78)
Postgraduate	30 (5.25)	28 (4.88)	38 (6.63)
Marital status				0.217	-
Single	173 (30.30)	177 (30.84)	152 (26.53)
Marriage	398 (69.70)	397 (69.16)	421 (73.47)
Suicide attempt				< 0.001	-
No	502 (87.92)	515 (89.72)	355 (61.95)
Yes	69 (12.08)	59 (10.28)	218 (38.05)
Comorbid anxiety				< 0.001	-
No	138 (24.17)	154 (26.83)	46 (8.03)
Yes	433 (75.83)	420 (73.17)	527 (91.97)
Psychotic symptoms				< 0.001	-
No	548 (95.97)	544 (94.77)	455 (79.41)
Yes	23 (4.03)	30 (5.23)	118 (20.59)

¹P value was adjusted for potential confounders, including age (years), sex and body mass index (kg/m²).

Table 2 Relationship between thyroid-stimulating hormone levels and suicide attempt in different models

Variable	Non-adjusted model [OR (95%CI), P value]	Adjust I model [OR (95%CI), P value]	Adjust II model [OR (95%CI), P value]
TSH (μIU/mL)	1.38 (1.31-1.45), < 0.0001	1.38 (1.31-1.45), < 0.0001	1.09 (1.01-1.17), 0.0268
TSH (μIU/mL) tertiles
Low	1.0	1.0	1.0
Middle	0.83 (0.58-1.21), 0.3328	0.83 (0.57-1.20), 0.3222	0.60 (0.40-0.91), 0.0159
High	4.47 (3.30-6.05), < 0.0001	4.42 (3.26-5.99), < 0.0001	1.29 (0.81-2.05), 0.2887

Non-adjusted model for: None. Adjust I model for: (1) Age (years); and (2) Gender. Adjust II model for: (1) Age (years); (2) Gender; (3) Hamilton Anxiety Scale; (4) Systolic pressure (mmHg); (5) Diastolic pressure (mmHg); (6) Anti-thyroglobulin (IU/L); (7) Thyroid peroxidase antibody (IU/L); (8) Fasting blood glucose (mmol/L); (9) Total cholesterol (mmol/L); (10) High-density lipoprotein cholesterol (mmol/L); (11) Triglycerides (mmol/L); (12) Low-density lipoprotein cholesterol (mmol/L); and (13) Body mass index (kg/m²). OR: Odds ratio; TSH: Thyroid-stimulating hormone.

Table 3 Threshold effect of thyroid-stimulating hormone levels and suicide attempt using a piecewise logistic regression model

Outcome	Suicide attempt [odds ratio (95%CI), P value]
Model I
Linear effect	1.09 (1.01-1.17), 0.0349
Model II
Inflection point (K)	5.43
< K slope 1	0.94 (0.82-1.07), 0.3386
> K slope 2	1.21 (1.08-1.36), 0.0009
Slope 2 - slope 1	1.29 (1.07-1.57), 0.0090
Predicted at K	-1.90 (-2.13 to -1.67)
Log likelihood ratio test	0.009

For exposure: Thyroid-stimulating hormone (μIU/mL). Adjusted for: (1) Age (years); (2) Gender; (3) Diastolic pressure (mmHg); (4) Systolic pressure (mmHg); (5) Hamilton Anxiety Scale; (6) Anti-thyroglobulin (IU/L); (7) Thyroid peroxidase antibody (IU/L); (8) Fasting blood glucose (mmol/L); (9) Total cholesterol (mmol/L); (10) High-density lipoprotein cholesterol (mmol/L); (11) Triglycerides (mmol/L); (12) Low-density lipoprotein cholesterol (mmol/L); (13) Body mass index (kg/m²); and (14) Hamilton Depression Scale continuous.

Table 4 Thyroid dysfunction prevalence, n (%)

Condition	Overall	Non-SA	SA
Subclinical hypothyroidism (TSH > 4.20 μIU/mL with normal FT4/FT3)	1034 (60.19)	771 (56.20)	263 (76.01)
Overt hypothyroidism (TSH > 10 μIU/mL with low FT4/FT3)	0 (0.00)	0 (0.00)	0 (0.00)

Thyroid dysfunction was defined using combined thyroid-stimulating hormone (TSH) and thyroid hormone criteria. Subclinical hypothyroidism was defined as TSH > 4.20 μIU/mL with free thyroxine and free triiodothyronine within the reference ranges. Overt hypothyroidism was defined as TSH > 10 μIU/mL with free thyroxine and/or free triiodothyronine below the lower limits of the reference ranges. FT3: Free triiodothyronine; FT4: Free thyroxine; SA: Suicide attempt; TSH: Thyroid-stimulating hormone.

Table 5 Relationship between free triiodothyronine/free thyroxine levels and suicide attempt in different models

Predictor	Unadjusted OR (95%CI), P value	Model I (age, sex) [OR (95%CI), P value]	Model II (fully adjusted) [OR (95%CI), P value]
Free triiodothyronine (pmol/L)	1.022 (0.869-1.203), 0.790	1.036 (0.879-1.220), 0.673	0.970 (0.801-1.175), 0.758
Free thyroxine (pmol/L)	0.997 (0.959-1.035), 0.858	0.998 (0.960-1.036), 0.903	0.980 (0.938-1.024), 0.360

Normal free triiodothyronine was defined as 3.1-6.8 pmol/L and normal free thyroxine as 10.38-23.21 pmol/L; low free triiodothyronine/free thyroxine was defined as values below the lower limits. Un-adjusted model for: None. Adjust I model for: (1) Age (years); and (2) Sex. Adjust II model for: (1) Age (years); (2) Sex; (3) Hamilton Anxiety Scale; (4) Systolic pressure (mmHg); (5) Diastolic pressure (mmHg); (6) Anti-thyroglobulin (IU/L); (7) Thyroid peroxidase antibody (IU/L); (8) Fasting blood glucose (mmol/L); (9) Total cholesterol (mmol/L); (10) High-density lipoprotein cholesterol (mmol/L); (11) Triglycerides (mmol/L); (12) Low-density lipoprotein cholesterol (mmol/L); and (13) Body mass index (kg/m²). OR: Odds ratio.