Table 2.

Observational Studies Measuring Tg in Relation to Iodine Status in Pregnant Women

Authors	Age (years)a; nb; country	Trimesters	UICc (μg/L)				Tgc (μg/L)				Findings	Comments
Pedersen et al. (38)	21–38; n=20; Denmark	3rd	52d				67				Suggested high Tg might be due to an increase in iodine intake in pregnancy	Women did not take iodine supplements.
Laurberg et al. (76)	NR; n=20; Denmark, Sweden, and Iceland	At term	Denmark			39	Denmark			29.7	Women living in Denmark had a significantly higher median Tg than those living in Sweden and Iceland (p<0.05)	No data on supplement use
			Sweden			78	Sweden			15.9
			Iceland			118	Iceland			15.9
Eltom et al. (78)	20–40; n=48; Sweden and Sudan	1st, 2nd, and 3rd		Trimesters				Trimesters			Sudanese women had a significantly higher median Tg than the Swedish women in the 1st (p<0.05), 2nd (p<0.001), and 3rd trimesters (p<0.01).	Women were followed throughout pregnancy; no data on supplement use
				1st	2nd	3rd		1st	2nd	3rd
			Swedish	89	89	76	Swedish	15.5	10.5	18.0
			Sudanese	38	25	38	Sudanese	27.5	25.0	30.0
Costeira et al. (79,93)e	29.9; n=118; Portugal	1st, 2nd and 3rd trimester, and 1 year PP	Trimester				Trimester				Tg in 1st and 2nd trimester increased from 11 to 13 μg/L in 3rd trimester	Women were followed throughout pregnancy; they did not take iodine supplements
			1st			65	1st			11.0
			2nd			57	2nd			11.0
			3rd			70	3rd			12.7
			1 year PP			40	1 year PP			9.7
Brucker-Davis et al. (74)	18–40; n=110; France	1st	116				17.4				Tg was not correlated with UIC	Women did not take iodine supplements
Raverot et al. (75)	15.3–45.7; n=228; France	1st, 2nd, and 3rd	Trimester				Trimester				Tg in the 1st, 2nd, or 3rd trimesters were not significantly different (p>0.05)	Women did not take iodine supplements
			1st			69	1st			16.6
			2nd			91	2nd			15.7
			3rd			91	3rd			16.2
Andersen et al. (37)	27.3; n=140; Denmark	At term	No supplements			NR	No supplements			29.36	Women taking supplements (i.e., 150 μg I/day) had a significantly lower Tg than those not taking supplements (p<0.001)
			Supplements			NR	Supplements			14.06
			All			41f	All			22.96
Brough et al. (77)	31; n=70; New Zealand	3rd trimester or breastfeeding for >3 weeks	3rd trimester			85	3rd trimester			15.9	Tg was not correlated with UIC in women in the 3rd trimester and at PP	70% pregnant women and 36% breastfeeding women used iodine supplements ranging from 100 to 150 μg I/day
			PP			74	PP			13.9

^aRange used unless mean reported.

^bOnly subjects with no known thyroid disease or negative for TgAb were included.

^cMedian used unless mean or geometric mean reported.

^dUIC reported as μg/g creatinine.

^eTg was reported in Costeira et al. (79); UIC and the data on supplement use were reported in Costeira et al. (93). These two studies were counted as one study (79).

^fGeometric mean.

I, iodine; PP, postpartum.