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Laurberg, Pedersen
Iodine nutrition in breast-fed infants is impaired by maternal smoking.Laurberg P, Nohr SB, Pedersen KM, Fuglsang E. J Clin Endocrinol Metab. 2004 Jan;89(1):181-7.
"Lack of iodine for
thyroid hormone formation during the fetal stage and/or the first
years of life may lead to developmental brain damage. During the
period of breastfeeding, thyroid function of the infant depends
on iodine in maternal milk. We studied healthy, pregnant women
admitted for delivery and their newborn infants. Cotinine in
urine and serum was used to classify mothers as smokers (n = 50)
or nonsmokers (n = 90). Smoking and nonsmoking mothers had
identical urinary iodine on d 5 after delivery, but smoking was
associated with reduced iodine content in breast milk (smokers
26.0 micro g/liter vs. nonsmokers 53.8 micro g/liter; geometric
mean, P < 0.001) and in the infants' urine (smokers 33.3 micro
g/liter, vs. nonsmokers 50.4 micro g/liter, P = 0.005). Results
were consistent in multivariate linear models and by logistic
regression analysis. The odds ratio for smoking vs. nonsmoking
mothers to have lower breast milk than urinary iodine content was
8.4 (95% confidence interval, 3.5-20.1). In smokers, iodine
transfer into breast milk correlated negatively to urinary
cotinine concentration. Smoking mothers had significantly higher
serum levels of thiocyanate, which may competitively inhibit the
sodium-iodide symporter responsible for iodide transport in the
lactating mammary gland. Smoking during the period of
breastfeeding increases the risk of iodine deficiency-induced
brain damage in the child. Women who breastfeed should not smoke,
but if they do, an extra iodine supplement should be considered."
Postpartum thyroid dysfunction in pregnant thyroid peroxidase antibody-positive women living in an area with mild to moderate iodine deficiency: is iodine supplementation safe?Nohr SB, Jorgensen A, Pedersen KM, Laurberg P. J Clin Endocrinol Metab. 2000 Sep;85(9):3191-8.
"In moderately iodine-deficient, pregnant, thyroid peroxidase antibody (TPO-Ab)-positive women the role of iodine supplementation in the development of postpartum thyroid dysfunction (PPTD) was studied in a placebo-controlled, randomized, double blind trial. Screening for TPO-Ab was performed in early pregnancy in a population of healthy pregnant Danish women with no previous diagnosed thyroid disease (prevalence, 117 of 1,284; 9.1%). The participants were randomized, stratified according to TPO-Ab level, to three groups. All participants received a daily vitamin and mineral tablet with 150 microg iodine or no iodine. The +/+ group received iodine during pregnancy and the postpartum period, the +/- group received iodine during pregnancy only, and the -/- group received no iodine supplementation. A total of 66 TPO-Ab positive women were followed, and in the postpartum period sera were collected at 8-week interval for biochemical evaluation of thyroid function and antibody level. Compliance was evaluated by 24-h urinary iodine measurements. PPTD developed in 55% of the participants. In 67% of the cases abnormal TSH was accompanied by abnormalities in thyroid hormones, whereas 33% had abnormal serum TSH only. There was no statistically significant difference in the frequency of PPTD in the three groups: +/+ group, 59% (95% confidence interval, 36-79%); +/- group, 60% (36-81%); and -/- group, 46% (26-67%). There were also no differences in the severity of the PPTD, as evaluated by duration and grade of deviation of TSH and thyroid hormones from normality. The occurrence, severity, and type of PPTD predominantly depended on the TPO-Ab level: TPO-Ab below 200 U/L at screening, 35% developed PPTD; TPO-Ab of 200-900 U/L, 54%; and TPO-Ab above 900 U/L, 75% developed PPTD. Women with low levels of antibodies predominantly remained euthyroid or had hyperthyroidism only, whereas women with high antibody levels had hyperthyroidism followed by hypothyroidism or hypothyroidism only. We conclude that iodine supplementation (150 microg) during pregnancy and the postpartum period to TPO-Ab-positive women living in an area with mild to moderate iodine deficiency did not induce or worsen PPTD. The study confirmed that screening for TPO-Ab in early pregnancy can predict women at high risk for development of PPTD."
Amelioration of some pregnancy-associated variations in thyroid function by iodine supplementation.Pedersen KM, Laurberg P, Iversen E, Knudsen PR, Gregersen HE, Rasmussen OS, Larsen KR, Eriksen GM, Johannesen PL. J Clin Endocrinol Metab. 1993 Oct;77(4):1078-83. [abstract only]
"Knowledge of the effect of differences in iodine intake levels on public health in areas with no endemic goiter is limited. Groups at risk when iodine intake is relatively low are pregnant and lactating women and their newborns. A prospective randomized study was performed to evaluate the effect of iodine supplementation in an area where the median daily iodine excretion in urine is around 50 micrograms. Fifty-four normal pregnant women were randomized to be controls or to receive 200 micrograms iodine/day from weeks 17-18 of pregnancy until 12 months after delivery. In the control group, serum TSH, serum thyroglobulin (Tg), and thyroid size showed significant increases during pregnancy. These variations were ameliorated by iodine supplementation. Iodine did not induce significant variations in serum T4, T3, or free T4. Cord blood Tg was much lower when the mother had received iodine, whereas TSH, T4, T3, and free T4 levels were unaltered. The results suggest that a relatively low iodine intake during pregnancy leads to thyroidal stress, with increases in Tg release and thyroid size. However, the thyroid gland is able to adapt and keep thyroid hormones in the mother and the child normal, at least under normal circumstances, as evaluated in the present study. It is not known whether this stress is sufficient to be of importance for late development of autonomous thyroid growth and function."
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