Areas Of Mild Iodine Deficiency Research Articles

Multifactor analysis of relationship between the biological exposure to iodine and hypothyroidism

To assess the relationship between the biological exposure to iodine and hypothyroidism. Logistic regression model was used to analyze the risk factors of hypothyroidism, according to the epidemiologic data of 3761 adults in 3 kinds of rural communities: mild iodine deficiency area (4 natural villages in Panshan County, Liaoning Province), more than adequate iodine (7 natural villages of Zhangwu County, Liaoning Province), and excessive iodine area (2 natural villages of Huanghua City, Hebei Province). More than adequate iodine and excessive iodine were independent risk factors of subclinical hypothyroidism (OR = 3.172 and 6.391, P < 0.05) and overt hypothyroidism (OR = 3.696 and 9.213, P < 0.05). When interactions of iodine exposure and thyroid peroxidase antibody (TPOAb) or thyroglobulin antibody (TgAb) were included, more than adequate iodine was still a risk factor of subclinical hypothyroidism (OR = 2.788, P < 0.01), but had no such effect on overt hypothyroidism. Interaction of more than adequate iodine and positive TgAb significantly affected subclinical hypothyroidism and overt hypothyroidism (OR = 2.656 and 3.347, P < 0.05). More than adequate and excessive iodine exposure are independent risk factors of hypothyroidism. The risk of hypothyroidism grows up and thyroid dysfunction becomes more serious with the increasing of the biological exposure to iodine.

Prospective Study of Post‐partum Thyroid Immune Dysfunctions in Type 1 Diabetic Women and in a Healthy Control Group Living in a Mild Iodine Deficient Area

Second to diabetes mellitus, thyroid diseases are the most common endocrinopathies seen in pregnancy. The incidence of post‐partum thyroid dysfunction (PPTD) in women with type 1 diabetes mellitus is three‐fold increased. We determined the incidence of thyroid abnormalities in a well‐defined group of young subjects with type 1 diabetes and in an age‐matched healthy controls during and six months after pregnancy in an area of mild iodine deficiency. Twenty‐five out of twenty‐eight pregnant women completed the study. Fifteen were affected by type 1 diabetes and ten were controls. Our protocol of study consisted of four evaluations of each subject: in the first, in the second trimester, at delivery and six months after. At each control the patients were submitted to physical examination, thyroid ultrasonography, and determination of fT3, fT4, TSH, Antithyroglobulin antibodies (TgAbs), Antithyroperoxidase antibodies (TPOAbs). The variation of thyroid volume is statistically significant in both the diabetics and in the controls during the different times of observations. Four out of the fifteen diabetic pregnant patients (27%) developed a thyroid disease: two cases of post‐partum thyroiditis (PPT) and two cases of euthyroid benign nodular goiter, as confirmed by cytological examination. Two out ten controls (20%) developed positive antibodies (TPO Abs and TgAbs) since the first observation and showed an autoimmune thyroiditis six months after delivery. Both of them showed a familial history of thyroid disease. Our study suggests that in an area of mild iodine deficiency the incidence of thyroid autoimmunity in pregnant women is similar, whether diabetic or not; moreover, thyroid volume is increasing in the diabetics as much as in the non diabetics during pregnancy.

Normal values for thyroid ultrasonography, goiter prevalence and urinary iodine concentration in schoolchildren of the Veneto Region, Italy.

Goiter prevalence in school-age children and median urinary iodine concentration (UIC) are the main indicators of iodine deficiency in a population. In areas of mild iodine deficiency, where goiters are small, ultrasound is preferable to physical examination to estimate goiter prevalence. The World Health Organization (WHO) has adopted thyroid volume ultrasonography results from a survey of European schoolchildren as an international reference, but these values have recently been questioned. The aims of the study were: a) to determine regional normal echographic reference values of thyroid volume in children aged between 11 and 14 yr in the Veneto Region, in North-East Italy; b) to determine goiter prevalence by physical and ultrasonographic examination; c) to determine UIC in this section of the population. A cross-sectional study was carried out on 1730 schoolchildren, aged between 11 and 14, living in towns in low-lying areas, in the valleys of the pre-Alps and in the mountains between 600 and 1200 m. Thyroid volume was evaluated by inspection and palpation using the WHO criteria. In 560 children thyroid volume was determined by ultrasound. UIC was measured in 1368 children. On physical examination a grade I goiter was found in 7.5% of children. No goiter grade II or grade III was found. The regional thyroid volume reference values by ultrasonography were similar, or slightly lower (5-20%), to the corresponding WHO reference values. Mean UIC was 148 +/- 110 microg/l, with no difference between lowlands and uplands; UIC values less than 100 microg/l were found in about 30-35% of the children. UIC was higher in children using iodized salt than in non-users. No correlation was found between thyroid volume by ultrasonography and UIC. Thyroid volume was found to be bigger in upland children than in those in low-lying areas, probably because of low iodine intake in people living in the mountains in previous generations. This data show that Veneto is not a iodine-deficient area, with no presence of endemic goiter. However, the great number of children with a UIC of less than 100 microg/l also suggests the use of iodized salt in the Veneto Region.

Thyroid peroxidase and thyroglobulin autoantibodies in a large survey of populations with mild and moderate iodine deficiency.

Autoimmune thyroiditis is one of the most common autoimmune disorders. Autoantibodies against the thyroid gland, with thyroid peroxidase antibody (TPO-Ab) and thyroglobulin antibody (Tg-Ab) as the most common autoantibodies, can often be demonstrated in serum in population surveys. In the present study we evaluated if TPO-Ab and Tg-Ab tend to develop in parallel or whether one or the other may be more prevalent in subsets of the population. In a cross-sectional comparative study, performed in two areas of Denmark with mild and moderate iodine deficiency, 4649 randomly selected subjects in age groups between 18 and 65 years were examined. Blood tests were analysed for TPO-Ab and Tg-Ab using assays based on the radioimmunoassay (RIA) technique. The participants answered questionnaires, were clinically examined and had urine samples collected. The overall prevalence rate of thyroid autoantibodies (TPO-Ab and/or Tg-Ab) was 18.8%. The prevalence rates of TPO-Ab and Tg-Ab were similar (13.1 vs. 13.0%). Both antibodies were more frequent in females than in males, and in females the prevalence rates increased with age. In the age group 60-65 years thyroid antibodies were more frequently measured in sera from moderate than from mild iodine-deficient area (P = 0.02), whereas no differences were seen in younger subjects. In 38.8% of participants with thyroid autoantibodies in serum, both antibodies were present. In sera with both TPO-Ab and Tg-Ab present the concentrations of the antibodies were generally higher than in sera with only one type of antibody present. The prevalence rates of TPO-Ab and Tg-Ab were similar in this large population survey. The results suggest that TPO-Ab and Tg-Ab predominantly develop due to a general alteration in the immune system, whereas specific antigenic mechanisms are probably of less importance. However, further studies are needed to clarify the mechanisms involved in the development of thyroid autoantibodies.

Changes in iodine metabolism during late pregnancy and lactation: a longitudinal study among Sudanese women.

To elucidate the persistence, or otherwise, of the pregnancy-related changes in the iodine metabolism and thyroid function in a population residing in an area of mild iodine deficiency in the Sudan. A longitudinal prospective cohort study involving pregnant women who were recruited during their third trimester of pregnancy and were followed up for up to nine months after delivery. The study was conducted among Sudanese women residing in the Omdurman area in Khartoum, an area with a total goitre rate of 17.5%. Forty-seven pregnant women were recruited during their third trimester of pregnancy. Their mean age and weight were 29+/-4.6 y and 62.4+/-8.7 kg, respectively. Age matched healthy non-pregnant women living in the same area (n=40) served as a control group. Serum levels of thyrotropin (TSH), thyroxine (T4), triiodothyronine (T3), thyroglobulin (Tg) and the urinary iodine concentration (UIC) were determined during the third trimester (first occasion), and subsequently at three months (second occasion), six months (third occasion) and nine months after delivery (fourth occasion). Control subjects provided corresponding samples on one occasion. UIC, TSH, Tg, FT4 and T3. During the third trimester of pregnancy the median UIC and the free T4 (FT4) were lower than in the control group (P<0. 0001, P<0.0001, respectively), while the median Tg was higher than in the controls (P<0.03). Three months post-partum maximum thyroidal stimulation was evident, with elevated serum levels of TSH and Tg (P<0.0001, P<0.03) and reduced UIC and serum T3 and FT4 (P<0.0004, P<0.0005, P<0.0001), compared with the control group. Nine months post-partum the thyroid function was restored to the pre-pregnancy state, and the median values of TSH, Tg, T3, FT4 and UIC did not differ significantly from those in the control group. Our study suggests that the reversibility of the pregnancy-induced changes in the iodine status and thyroid function to the pre-pregnancy levels may depend on the iodine status of the mother during and after pregnancy. The thyroidal stress during the first three months of the post-partum period, which is partially due to the iodine loss in the breast milk, justifies further detailed studies to assess the iodine content of the breast milk and the role of breast milk as a vehicle for iodine supply of infants in situations of iodine deficiency. This study was supported by a grant from the Swedish Agency for Research Co-operation with Developing Countries.

Urinary iodine excretion in Estonian children

Recently, Mityukova et al. (1) reported the results of urinary iodine excretion in Belarus children. We would like to report the results of a similar study carried out in Estonia in 1995. Estonia is located about 700 km to the north of Belarus. Historically, Estonia has been an area of mild iodine deficiency, especially the south-eastern part of the country (2, 3). In the beginning of the 1960s, it was concluded that the iodine concentration of phreatic water was such that Estonia could be classified as a biogeochemical area with moderate iodine deficiency (3). Only in the northern parts of Estonia were the phreatic waters found to be relatively abundant in iodine (3); the success of iodine prophylaxis in reducing goitre prevalence among school children of the south-eastern regions of the country has confirmed this (4). Iodine prophylaxis has been neglected in Estonia for several years. There have been no recent investigations on iodine consumption in Estonia and this study was carried out because the urinary iodine level is a good indicator of dietary iodine intake (5).

Mild iodine deficiency during fetal/neonatal life and neuropsychological impairment in Tuscany

The neuropsychological performance of schoolchildren living in areas with present and past iodine deficiency in Tuscany was investigated. Children were submitted to: a) block design subtest of the Wechsler Intelligence Scale for Children-Revised (WISC-R) and a modified version of the WISC-R coding subtest which evaluate the general neuropsychological and cognitive performance, independently from familial cultural background; b) simple reaction time (RT) session which evaluates the efficiency of the whole information processing and nervous transmission mechanisms. Neuropsychological performance was tested in 107 children living in Borgo a Mozzano, an area of mild iodine deficiency (IDA) with a median urinary iodine excretion (UIE) of 64 micrograms/L (mean +/- SD: 80.1 +/- 57). One hundred and six sex and age-matched children living in Marina di Pisa, an iodine sufficient coastal village of Tuscany (ISA) with a median UIE of 142 micrograms/L (mean +/- SD: 173 +/- 95) were used as controls. Tests for neuropsychological performance were performed in 57 children living in the village of Vagli, an area with past iodine deficiency (PIDA): 30 children born before iodine prophylaxis (Group 1), when the median UIE was 32 micrograms/L (mean +/- SD: 47 +/- 22), 27 children born after the institution of iodine prophylaxis (Group 2), when the median UIE was 109 micrograms/L (mean +/- SD: 130 +/- 73). Sex and age-matched ISA-children were used as controls for each group. RTs were significantly delayed (p < 0.05) in IDA than in ISA children, while block design and coding subtests showed no significant difference.(ABSTRACT TRUNCATED AT 250 WORDS)

Thyroid function and thyroid size in normal pregnant women living in an iodine replete area.

The interpretation of the changes in thyroid hormone concentrations during normal pregnancy is a matter of debate involving, in some geographical regions, enhanced thyroid activity in early pregnancy and a hypothyroid state in the third trimester. A clinically detectable increase in thyroid size has been found in areas of mild iodine deficiency ('goitre of pregnancy'), but not in iodine replete areas. A prospective study. We have studied thyroid size and function in normal pregnant women living in an iodine replete area. Healthy women before and during a normal pregnancy resulting from artificial insemination (n = 10) and other women during the normal menstrual cycle (n = 11), in the iodine replete area of Amsterdam. Thyroid volume was measured by ultrasonography. Plasma T4, free T3, free reverse T3, TSH, thyroxine binding globulin, hCG, progesterone and thyroid autoantibodies were measured. Thyroid volume did not change during pregnancy (data given before pregnancy and during 1st, 2nd and 3rd trimesters, respectively: 10.3 +/- 5.1, 10.6 +/- 4.4, 9.6 +/- 3.8 and 9.4 +/- 3.0 ml, NS). Free T4 and free T3 levels declined during pregnancy (13.7 +/- 2.0, 13.5 +/- 4.1, 11.2 +/- 2.8, 10.2 +/- 1.6 pmol/l, P = 0.005; 4.55 +/- 0.63, 4.64 +/- 0.88, 3.72 +/- 0.67 and 4.01 +/- 0.75 pmol/l, P = 0.003), whereas free reverse T3 levels increased during pregnancy (0.16 +/- 0.04, 0.19 +/- 0.07, 0.14 +/- 0.03 and 0.20 +/- 0.07 pmol/l, P = 0.001). Thyroglobulin levels remained unchanged. Thyroid hormones and thyroid volume did not differ between follicular and luteal phases of the menstrual cycle. Thyroid volume does not increase during pregnancy in iodine-replete areas. The decrease in free T4 and free T3 and the increase in free reverse T3 concentrations during pregnancy resemble the changes in thyroid hormones seen in non-thyroidal illness. This could be a physiological adaptation enabling energy conservation during the high metabolic demands of pregnancy.

Postpartum thyroid dysfunction in an Italian population residing in an area of mild iodine deficiency

We have evaluated the occurrence of postpartum thyroid dysfunction (PPTD) in a group of 372 women residing in area of mild iodine deficiency. Thyroid function and autoimmune status were evaluated by means serum T4, T3, TSH measurement and detecting the presence of positive antithyroglobulin antibodies (AbTg), antimicrosomal antibodies (AbM) and thyroid-peroxidase antibodies (AbTPO) titers in women at parturition, at 1, 3, 6 and 12 months postpartum. New onset transient hypothyroidism occurred in 6.4% of women whereas transient thyrotoxicosis in only 1.8% of women. Transient hypothyroidism was not preceded by thyrotoxicosis as indicated by thyroid function tests and serum Tg concentrations. At parturition, the positivity of AbM and AbTPO titers and the presence of goiter appeared to be a risk factors for the development of PPTD.

Thyroid volume of East Slovakian adolescents determined by ultrasound 40 years after the introduction of iodized salt.

Thyroid volume was examined by ultrasonography in 207 boys and 220 girls aged 15-16 years from East Slovakia and it was found that 49.3% of the boys and 52.3% of the girls had thyroids between 10 and 15 ml. These thyroid volumes resemble those found in school children from areas of mild iodine deficiency (e.g. FRG) and are twice as large as those reported from Sweden, where iodine intake is sufficient. The findings were compared to these reported by others in 1949-53 before the introduction of iodine prophylaxis. It may be concluded that 40 years of goiter prophylaxis with iodized salt, though resulting in urinary excretion of approximately 100 micrograms/24 hr (as found by others in 1984), abolished large and medium size goiters in adolescents and decreased a prevalence of goiter grade I to about 25 percent, but appeared still to be insufficient to prevent goiter grade I completely.

Treatment of amiodarone associated thyrotoxicosis by simultaneous administration of potassium perchlorate and methimazole.

Amiodarone iodine induced thyrotoxicosis occurs frequently in patients residing in areas of mild iodine deficiency and in patients with preexisting goiter. Drug therapy of the hyperthyroidism is often unsuccessful. Twenty-three patients with amiodarone induced thyrotoxicosis were either not treated, treated with 40 mg methimazole daily or with methimazole and 1 gm potassium perchlorate daily for up to 40 days and then with methimazole alone. Thyrotoxicosis was more likely to spontaneously remit in patients without goiter. Therapy with methimazole alone was unsuccessful in inducing euthyroidism in 5 patients with goiter. However, combined therapy with methimazole and potassium perchlorate rapidly alleviated hyperthyroidism in almost all patients with goiter. This drug combination is successful because perchlorate inhibits the active transport of iodine into the thyroid and methimazole blocks the intrathyroidal synthesis of thyroid hormones.