Table 2.

Biomarkers of Exposure and Thyroid Function and Exposure Markers Across Pregnancy

	First trimester (n = 27)			Second trimester (n = 82)			Third trimester (n = 146)
Thyroid and exposure markers	Mean ± SD	Median	[Range]	Mean ± SD	Median	[Range]	Mean ± SD	Median	[Range]	p-Valuea
Thyroid markers in serum
TSH (mIU/L)	1.7 ± 1.1	1.4	[0.34–4.4]	1.9 ± 1.4	1.7	[0.32–10]	2.3 ± 1.6	2.1	[0.060–17]	0.0033
fT4( pmol/L)	16 ± 2.3	16	[13–20]	14 ± 1.8	14	[11–18]	13 ± 1.6	13	[9.5–17]	<0.001
T4 (nmol/L)	160 ± 32	155	[109–236]	153 ± 25	147	[87–201]	142 ± 24	139	[84–201]	0.0011
fT3 (pmol/L)	5.1 ± 0.62	5.1	[4.1–6.4]	4.7 ± 0.45	4.6	[3.6–5.7]	4.2 ± 0.47	4.2	[3–6.2]	<0.001
T3 (nmol/L)	2.6 ± 0.43	2.6	[2–3.4]	2.8 ± 0.43	2.8	[1.3–3.7]	2.7 ± 0.48	2.7	[1.2–5.2]	0.10
Thyroglobulin (μg/L)	12 ± 13	9.8	[0.5–53]	13 ± 9.0	11	[0.10–49]	16 ± 14	13	[0.30–107]	0.062
Transthyretin (mg/L)	214 ± 45	205	[100–280]	211 ± 43	210	[80–340]	205 ± 53	205	[52–350]	0.41
Exposure biomarkers
Blood lithium (μg/L)	23 ± 14	21	[4.3–55]	26 ± 19	23	[2.2–145]	29 ± 18	26	[1.9–109]	0.09
Urinary lithium (μg/L)	1372 ± 937	1117	[206–3903]	1634 ± 998	1398	[143–4523]	1714 ± 1065	1465	[105–5185]	0.13
Blood cesium (μg/L)	140 ± 73	132	[11–293]	132 ± 114	107	[2.5–659]	122 ± 98	111	[3.9–711]	0.16
Urinary cesium (μg/L)	510 ± 243	483	[45–1048]	530 ± 397	463	[14–2248]	492 ± 309	472	[17–1748]	0.79
Urinary iodine (μg/L)	154 ± 108	131	[49–575]	171 ± 188	121	[43–1490]	157 ± 121	115	[35–708]	0.87
Serum selenium (μg/L)	92 ± 8.9	92	[73–115]	91 ± 13	89	[64–131]	83 ± 15	81	[50–137]	<0.001

^aComparison across trimesters based on Kruskal-Wallis rank test.

TSH, thyrotropin; fT4, free thyroxine; T4, total thyroxine; fT3, free triiodothyronine; T3, total triiodothyronine.