Thyroglobulin is a sensitive measure of both deficient and excess iodine intakes in children and indicates no adverse effects on thyroid function in the UIC range of 100-299 μg/L: a UNICEF/ICCIDD study group report.
BACKGROUND
The median urinary iodine concentration (UIC) is a biomarker of iodine intake. According to the World Health Organization, a median UIC in the range 100-199 μg/L indicates adequate and 200-299 μg/L more than adequate intake. Thyroglobulin (Tg) may be a promising functional biomarker of both iodine deficiency and excess.


OBJECTIVE
Using a standardized dried blood spots-Tg assay in children, we evaluated the Tg response to both low- and high-iodine intake and estimated the population cutoff point for iodine deficiency or excess. Also, we compared thyroid functions within the UIC ranges of 100-199 vs 200-299 μg/L.


METHODS
We conducted a cross-sectional study in primary schools in 12 countries.


METHODS
SUBJECTS were 6 to 12 years old (n = 2512).


METHODS
We measured UIC, TSH, total T4, Tg, and thyroid antibodies.


RESULTS
Over a range of iodine intakes from severely deficient to excessive, Tg concentrations showed a clear U-shaped curve. Compared with iodine-sufficient children, there was a significantly higher prevalence of elevated Tg values in children with iodine deficiency (UIC <100 μg/L) and iodine excess (UIC >300 μg/L). There was no significant change in the prevalence of elevated Tg, TSH, T4, or thyroid antibodies comparing children within the UIC ranges of 100-199 vs 200-299 μg/L.


CONCLUSIONS
In school-aged children, 1) Tg is a sensitive indicator of both low and excess iodine intake; 2) a median Tg of <13 μg/L and/or <3% of Tg values >40 μg/L indicates iodine sufficiency in the population; 3) the acceptable range of median UIC in monitoring iodized salt programs could be widened to a single category of sufficient iodine intake from 100 to 299 μg/L.
Human Nutrition Laboratory and Secretariat of International Council for Control of Iodine Deficiency Disorders (ICCIDD) Global Network, Swiss Federal Institute of Technology (ETH), 8092 Zürich, Switzerland. michael.zimmermann@hest.ethz.ch
Michael B
MB
Zimmermann
Isabelle
I
Aeberli
Maria
M
Andersson
Vincent
V
Assey
Jorge A Jara
JA
Yorg
Pieter
P
Jooste
Tomislav
T
Jukić
Djoko
D
Kartono
Zvonko
Z
Kusić
Eduardo
E
Pretell
Teofilo O L
TO
San Luis
Juliawati
J
Untoro
Arnold
A
Timmer
D001323:Autoantibodies / Q000097:blood; D015415:Biomarkers / Q000097:blood / Q000652:urine; D002648:Child; D003430:Cross-Sectional Studies; D059788:Dried Blood Spot Testing; D005260:Female; D014943:Global Health; D006801:Humans; D007455:Iodine / Q000008:administration & dosage / Q000009:adverse effects / Q000172:deficiency* / Q000652:urine*; D008297:Male; D015995:Prevalence; D016036:Seroepidemiologic Studies; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage / Q000009:adverse effects; D013954:Thyroglobulin / Q000097:blood*; D013961:Thyroid Gland / Q000187:drug effects / Q000502:physiology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014131:Trace Elements / Q000172:deficiency / Q000652:urine; D014480:United Nations
D001323:Autoantibodies; D015415:Biomarkers; D017673:Sodium Chloride, Dietary; D014131:Trace Elements; C034024:iodized salt; D013972:Thyrotropin; D013954:Thyroglobulin; D007455:Iodine; D013974:Thyroxine