Table 2. Serum TSH and fT4 Concentrations in the Total Sample, the Disease-Free Population and the Reference Population in Korea National Health and Nutrition Examination Survey (2013 to 2015).

Variable	Total sample			Disease-free populationa			Reference populationb
	Total	Male	Female	Total	Male	Female	Total	Male	Female
TSH, mIU/L
2.5th Percentile	0.51	0.59	0.37	0.57	0.61	0.55	0.62	0.63	0.60
25th Percentile	1.53	1.48	1.59	1.55	1.49	1.62	1.55	1.49	1.62
Median	2.25	2.17	2.36	2.26	2.17	2.37	2.23	2.15	2.31
75th Percentile	3.30	3.08	3.59	3.28	3.07	3.57	3.18	3.02	3.35
97.5th Percentile	7.61	6.94	8.45	7.49	6.83	8.18	6.86	6.44	7.21
fT4, ng/dL
2.5th Percentile	0.91	0.96	0.87	0.92	0.96	0.88	0.96	0.99	0.94
25th Percentile	1.12	1.16	1.08	1.12	1.16	1.08	1.13	1.16	1.09
Median	1.23	1.28	1.19	1.23	1.27	1.18	1.24	1.28	1.19
75th Percentile	1.35	1.40	1.30	1.35	1.40	1.29	1.35	1.40	1.30
97.5th Percentile	1.63	1.65	1.58	1.61	1.64	1.55	1.60	1.61	1.53

TSH, thyroid stimulating hormone; fT4, free thyroxine.

^aThe disease-free population was defined as subjects with no prior history of thyroid disease and no history of taking medications that could influence thyroid function; ^bThe reference population was defined as subjects with no prior history of thyroid disease, no history of taking medications that could influence thyroid function, no family history of thyroid disease, negative anti-thyroid peroxidase antibody results, and serum fT4 levels in the reference range (0.89 to 1.76 ng/dL).