Correlation between diabetic peripheral neuropathy and thyroid hormone sensitivity in elderly patients with type 2 diabetes mellitus

Table 1 Comparison of the general characteristics and biochemical indices between the two groups, n (%)

Variables	DPN (n = 161)	NDPN (n = 95)	P value
Age (year)1	67.0 (63.0-70.0)	66.0 (63.0-70.0)	0.976
Sex (female)	77 (47.8)	56 (58.9)	0.112
Duration of diabetes (years)2	15.46 ± 8.23	15.70 ± 7.79	0.820
BMI (kg/m2)1	24.97 (23.2-27.62)	24.40 (22.50-26.04)	0.137
FT3 (pg/mL)2	2.97 ± 0.31	3.03 ± 0.34	0.118
FT4 (ng/dL)1	1.16 (1.07-1.32)	1.12 (1.05-1.28)	0.158
TSH (IU/mL)1	1.81 (1.21-2.67)	1.84 (1.40-2.78)	0.646
TT4RI1	27.61 (18.57-38.48)	27.73 (20.74-39.06)	0.869
TSHI2	2.64 ± 0.57	2.62 ± 0.61	0.755
FT3/FT42	0.302 ± 0.053	0.316 ± 0.049	0.040
TFQI1	-0.10 (-0.32-0.14)	-0.16 (-0.31-0.06)	0.287
ALB (g/L)1	40.00 (38.00-42.00)	40.0 (38.00-42.00)	0.186
UA (umol/L)1	346.00 (291.00-400.00)	327.00 (263.00-388.00)	0.276
FBG (mol/L)1	7.40 (5.90-9.50)	6.95 (5.90-8.70)	0.185
TC (mmol/L)1	4.10 (3.33-5.00)	4.25 (3.42-4.98)	0.404
TG (mmol/L)1	1.35 (0.98-1.93)	1.25 (0.88-1.66)	0.198
LDL-C (mmol/L)1	2.27 (1.73-3.08)	2.39 (1.69-3.07)	0.691
HDL-C (mmol/L)1	1.03 (0.92-1.21)	1.19 (1.01-1.36)	0.001
HbA1c (%)1/(mmol/mol)	8.60 (7.50-10.20)/70 (58-88)	8.60 (7.00-9.60)/70 (53-81)	0.073
Hypertension	118 (73.2)	59 (62.1)	0.083
Smoking	66 (40.9)	29 (30.5)	0.123
Drinking	56 (34.1)	27 (28.4)	0.417

¹The Kruskal-Wallis test was used to analyze non-normally distributed data.

²The independent samples t-test was used to compare data that conformed to a normal distribution.

Values are expressed as the median (P25-P75), mean ± SD, or numbers and percentages. The χ² test was used to compare sex, hypertension, current smoking, and alcohol intake. BMI: Body mass index; DPN: Diabetic peripheral neuropathy; FT₃: Free triiodothyronine; FT₄: Free thyroxine; FT₃/FT₄: Free triiodothyronine/free thyroxine ratio; HDL-C: High-density lipoprotein cholesterol; LDL-C: Low-density lipoprotein cholesterol; NDPN: Non-diabetic peripheral neuropathy; TC: Total cholesterol; TG: Triglycerides; TSH: Thyroid-stimulating hormone; TSHI: Thyroid-stimulating hormone index; TT4RI: Thyroxine resistance index; TFQI: Thyroid feedback quantile index; UA: Uric acid.

Table 2 Correlation analysis between free triiodothyronine/free thyroxine levels and neuro conductivity and skin conductance indicators

	r	P value
Median nerve motor latency (millisecond)	-0.093	0.139
Median nerve motor amplitude (mV)	0.076	0.226
Median nerve motor velocity (m/second)	0.156	0.013
Common peroneal nerve motor latency (millisecond)	0.012	0.848
Common peroneal nerve motor amplitude (mV)	-0.027	0.670
Common peroneal nerve motor velocity (m/second)	0.027	0.667
Median nerve sensory latency (millisecond)	-0.103	0.101
Median nerve sensory amplitude (mV)	0.107	0.089
Median nerve sensory velocity (m/second)	0.098	0.117
Common peroneal nerve sensory latency (millisecond)	-0.028	0.662
Common peroneal nerve sensory amplitude (mV)	0.076	0.225
Common peroneal nerve sensory velocity (m/second)	0.040	0.526
F-min (millisecond)	-0.084	0.186
M-latency (millisecond)	-0.088	0.161
Two-legged ESC (microsecond)	0.177	0.005
Two-handed ESC (microsecond)	0.154	0.015

F-min: Minimum latency of the F-wave; M-latency: Median nerve motor evoked potential latency; ESC: Electrochemical skin conductance.

Table 3 Association between free triiodothyronine/free thyroxine stratification and neuro conductivity, skin conductance indicators

		Odds ratio	95%CI	P value
Model 1	Two-legged ESC (microsecond)	1.017	1.004-1.031	0.013
Model 2	Two-legged ESC (microsecond)	1.019	1.005-1.034	0.007
	Common peroneal nerve sensory amplitude (mV)	1.310	1.008-1.703	0.043

ESC: Electrochemical skin conductance.