Association between Urinary Iodine Concentration and Thyroid Nodules in Adults: A Cross-Sectional Study in China

Table 2

Threshold effect analysis for the relationship between UIC and the risk of thyroid nodules^a.

Models	Male		Female
	Risk of TNs adjusted OR (95% CI)		Risk of TNs adjusted OR (95% CI)
Model I
One-line slope	0.92 (0.86, 0.97)	0.006	0.95 (0.91, 0.99)	0.023
Model II
Turning point (K)	5.27		4.79
<K slope 1	0.87 (0.80, 0.94)	<0.001	0.92 (0.86, 0.98)	0.008
>K slope 2	1.25 (0.98, 1.60)	0.076	1.06 (0.91, 1.23)	0.478
Slope 2–slope 1	1.44 (1.08, 1.92)	0.013	1.15 (0.95, 1.39)	0.150
Predicted at K	-2.50 (-2.75, -2.25)		-2.01 (-2.19, -1.83)
LRT test	0.018		0.156

^aAdjusted for age, educational status, smoking status, type of salt used, family history of thyroid diseases, systolic pressure, body mass index, and waist circumference. Model I, linear analysis; Model II, nonlinear analysis; LRT test: likelihood ratio test; TNs: thyroid nodules. The value of OR corresponded to per 100 units change of urinary iodine concentration.