Table 3.

Infant UIC, BMIC and infant thyroid function tests (TSH, fT3 and fT4)

(Numbers and percentage; mean values and standard deviations)

	3 months		6 months		11 months
Variable	n	Value	n	Value	n	Value
UIC (µg/l)	108		90		91
Median		82		110		110
p25–p75		54–140		78–190		77–170
Mean		107		147		141
sd		77		102		104
< 100 µg/l (%)		61%		41%		37%
< 50 µg/l (%)		19%		7%		9%
BMIC (µg/l)	99			–		–
Median		77
p25–p75		55–130
Mean		91
sd		48
< 100 µg/l (%)		64%
< 50 µg/l (%)		13%
TSH (mIU/l)	47		53
Mean		2·4		1·9
sd		1·2		0·87
p10–p90		1·1–4·6		0·92–3·4
min–max		0·80–5·5		0·78–3·9
< ref. range* (1.1)
n		3		7
%		6		13
> ref· range* (8.2)
n		0		0
%		0		0
fT3 (pmol/l)	47		52			–
Mean		6·8		6·7
sd		0·74		0·64
p10–p90		5·9–7·8		5·9–7·5
min–max		5·2–8·5		5·2–8·3
< ref. range* (4.5)
n		0		0
%		0		0
> ref. range* (8.0)
n		3		2
%		6		4
fT4 (pmol/l)	47		52			–
Mean		17·7		17·6
sd		1·8		1·6
p10–p90		15·6–20·0		15·2–20·0
min–max		13·0–21·0		14·5–21·6
< ref. range* (11.0)
n		0		0
%		0		0
> ref. range* (23.0)
n		0		0
%		0		0

UIC, urinary iodine concentration; BMIC, breast milk iodine concentration; TSH, thyroid-stimulating hormone; fT3, free triiodothyronine; fT4, free thyroxine.

^*Reference ranges derived from laboratory⁽²²⁾. TSH (1–12 months): 1·1–8·2 mµ/l; fT3 (0–9 years): 4·5–8·0 pmol/l; fT4 (0–12 months): 11·0–23·0 pmol/l.