Vitamin A supplementation in iodine-deficient African children decreases thyrotropin stimulation of the thyroid and reduces the goiter rate.
BACKGROUND
Vitamin A (VA) deficiency (VAD) and iodine deficiency (ID) often coexist in children in Africa. VAD may affect thyroid function and the response to iodine prophylaxis.


OBJECTIVE
The aim was to investigate the effects of supplementation with iodine or VA alone, and in combination, in children with concurrent VAD and ID.


METHODS
A 6-mo randomized, double-blind, 2 x 2 intervention trial was conducted in 5-14 y-old South African children (n = 404), who, on average, had mild-to-moderate VAD and ID. At baseline and after 3 mo, children received 1) iodine (191 mg I as oral iodized oil) + placebo (IS group), 2) VA (200000 IU VA as retinyl palmitate) + placebo (VAS group), 3) both iodine and VA (IS+VAS group), or 4) placebo. At baseline, 3 mo, and 6 mo, urinary iodine (UI), thyroid volume, thyrotropin (thyroid-stimulating hormone; TSH), total thyroxine (TT(4)), thyroglobulin, serum retinol (SR), and retinol-binding protein (RBP) were measured.


RESULTS
SR and RBP increased significantly with VA supplementation (P < 0.05). For UI, SR, and RBP, there were no significant treatment interactions between iodine and vitamin A. The 3-factor and all three 2-factor interactions were significant for thyroid volume, TSH, and thyroglobulin (P < 0.001), whereas none of these interactions were significant for TT(4). There was a clear effect of VAS without IS on TSH, thyroglobulin, and thyroid volume; all 3 variables decreased significantly (P < 0.05).


CONCLUSIONS
Iodine prophylaxis is effective in controlling ID in areas of poor vitamin A status. VA supplements are effective in treating VAD in areas of mild ID and have an additional benefit-through suppression of the pituitary TSHbeta gene, VAS can decrease excess TSH stimulation of the thyroid and thereby reduce the risk of goiter and its sequelae.
Zimmermann
Michael B
MB
Laboratory for Human Nutrition, Swiss Federal Institute of Technology, Zürich, Switzerland. michael.zimmermann@ilw.agrl.ethz.ch
Jooste
Pieter L
PL
Mabapa
Ngoako Solomon
NS
Schoeman
Serena
S
Biebinger
Ralf
R
Mushaphi
Linda F
LF
Mbhenyane
Xikombiso
X
D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D006042:Goiter / Q000453:epidemiology / Q000517:prevention & control*; D006801:Humans; D007455:Iodine / Q000008:administration & dosage* / Q000172:deficiency*; D008297:Male; D012177:Retinol-Binding Proteins; D013019:South Africa / Q000453:epidemiology; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D013963:Thyroid Hormones / Q000097:blood; D013972:Thyrotropin / Q000494:pharmacology; D016896:Treatment Outcome; D014801:Vitamin A / Q000008:administration & dosage* / Q000097:blood; D014802:Vitamin A Deficiency / Q000188:drug therapy* / Q000453:epidemiology
D012177:Retinol-Binding Proteins; D013963:Thyroid Hormones; D014801:Vitamin A; D013972:Thyrotropin; D007455:Iodine