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BACKGROUND: Thyroid dysfunction is associated with negative neonatal and obstetric outcomes. Large differences in thyroid function reference intervals exist across different populations. These differences can be explained by population-specific factors, such as iodine status. Many countries in Latin America report iodine sufficiency, but relatively few countries have published up-to-date data on iodine levels and thyroid function in the overall population, and especially in pregnant women. We evaluated the iodine status of pregnant women in Chile and determined thyroid hormone reference ranges in this population. METHODS: This was a prospective observational study of healthy Chilean women at their first prenatal visit before week 14. Thyroid-stimulating hormone (TSH), total thyroxine (T4), free T4, antithyroid peroxidase antibody (TPOAb), and iodine levels from spot urine samples were measured. Iodine status and the reference ranges for TSH were calculated. RESULTS: A total of 1,022 pregnant women in the first trimester were selected. Urinary iodine levels were measured in 302 randomly-selected women. The median urinary iodine concentration was 173.45 µg/L (interquartile range, 108.11 to 249.35).The reference ranges of TSH were calculated in 670 patients selected according to the National Academy of Clinical Biochemistry guidelines. The median TSH level was 1.88 µIU/mL (2.5th percentile: 0.13 to 97.5th percentile: 5.37). Using the reference range in the 1,022 women, the prevalence of clinical hypothyroidism was 1.76%, and that of subclinical hypothyroidism was 3.92%. TPOAb positivity was more common in women with TSH levels above 3.5 µIU/mL. CONCLUSION: We found adequate iodine intake and a right-shifted distribution of serum TSH levels in pregnant women in Chile. The prevalence of hypothyroidism in our sample of pregnant women was higher than has been described in the literature.

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BACKGROUND: Early onset of menarche has been linked to prevalence of obesity; however, this may differ for indigenous females. OBJECTIVE: To analyse the relationship between age of menarche and nutritional status among indigenous and non-indigenous girls. METHOD: The design of this study was cross-sectional. Date of menarche was determined through interviews, and all responses were confirmed by the girls' mothers. A total of 8504 adolescents were screened for recent menarche. One hundred and thirty-one girls of Mapuche (indigenous) and 143 girls of Chilean-Spanish background were identified and evaluated by anthropometric measurements. RESULTS: Median age of menarche was 150 months, interquartile range (IR) 143-157 in indigenous, and 145.5 months, IR 139-153 in non-indigenous girls (p = 0.04). The indigenous females showed a higher prevalence of overweight (36.4% vs 23.1%), although the frequency of obesity was similar (16.8% vs 16.3%). For indigenous girls, age of menarche was delayed by 2.69 months (confidence intervals (CI) -0.38 to 5.77). It was observed that girls with overweight experienced age of menarche 7.59 months earlier than those with normal weight, CI -10.78 to -4.41. In the analysis of obesity, the effect on age of menarche was similar, with onset 7.53 months earlier than for the normal weight, CI -11.34 to -3.72. CONCLUSION: Age of menarche is younger than has been previously reported and occurs earlier in girls with overweight and obesity, while being indigenous was not related.

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BACKGROUND: Improvements in environmental conditions may result in an earlier onset of thelarche. However, its onset is not homogeneous among different population groups. AIM: To assess the relationship between nutritional status, ethnicity and age of thelarche. MATERIAL AND METHODS: Cross-sectional study of girls in second through sixth grade, attending 165 schools located in Chile's Araucania region. Of these, 231 girls who presented thelarche (breast button) were selected. The girls' surnames were used to identify their ethnicity: indigenous had three or four last names of Mapuche indigenous origin (n =113), while non-indigenous were those who only had Chilean-Spanish last names (n =118). Weight, height, waist circumference and skinfold thicknesses were measured and socio-economic background information was collected through a home interview. RESULTS: The median age of thelarche was 10 years and 4 months, regardless of ethnic group. Multivariant models showed that an increase of one z score unit of body mass index (BMI) decreased the median age of thelarche by 5.6 months (CI: -7.24 to -3.90), controlling for the effect of different covariables. A decrease in one z score of height retards the median age of thelarche by 5.5 months (CI: 4.02 to 6.98). Ethnicity did not influence the age of thelarche. CONCLUSIONS: The age of thelarche found by us is similar to that reported in international studies, it comes earlier as weight increases, is delayed as height decreases and is not related to ethnicity.

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Background: Improvements in environmental conditions may result in an earlier onset of thelarche. However, its onset is not homogeneous among different population groups. Aim: To assess the relationship between nutritional status, ethnicity and age of thelarche. Material and methods: Cross-sectional study of girls in second through sixth grade, attending 165 schools located in Chile's Araucania region. Of these, 231 girls who presented thelarche (breast button) were selected. The girls' surnames were used to identify their ethncity: indigenous had three or four last names of Mapuche indigenous origin (n =113), while non-indigenous were those who only had Chilean-Spanish last names (n =118). Weight, height, waist circumference and skinfold thicknesses were measured and socio-economic background information was collected through a home interview. Results: The median age of thelarche was 10 years and 4 months, regardless of ethnic group. Multivariant models showed that an increase of one z score unit of body mass index (BMI) decreased the median age of thelarche by 5.6 months (CI: -7.24 to -3.90), controlling for the effect of different covariables. A decrease in one z score of height retards the median age of thelarche by 5.5 months (CI: 4.02 to 6.98). Ethnicity did not influence the age of thelarche. Conclusions: The age of thelarche found by us is similar to that reported in international studies, it comes earlier as weight increases, is delayed as height decreases and is not related to ethnicity.

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Background: Body mass index (BMI) is the recommended parameter to assess the nutritional status of subjects aged less than 20 years. However, during puberty the correlation between BMI and fat mass decreases notably. Therefore, the use of BMI for the diagnosis of obesity during puberty may be misleading. Aim: To evaluate the variations of the BMI during puberty according to chronological and biological ages. Material and methods: Descriptive cross sectional study in school age children of elementary and high schools (4,531 males and 5,326 females) representing all socioeconomic strata of 4 regions of Chile. BMI was calculated from weight and height measurements (W/H2) and pubertal development was evaluated according to Tanner stages. The sample selected to evaluate the variations of BMI according to chronological age and pubertal stages consisted in 3,913 females aged 8-14 years and 2,494 males aged 10-16 years. Analyses of variance (F test) and Tukey HSD test were used to compare mean BMI according to chronological and biological ages. Results: The age of onset of puberty (Tanner Stages IB2 and G2) varied greatly, from 8 to 14 years in females and 10 to 16 years in males. Mean BMI in a specific stage of pubertal development did not show significant differences according to age in both sexes. However, there were significant differences (p <0.05) in mean BMI when comparing children of the same chronological age but in different Tanner stages. Per each stage of Tanner development, BMI increased 1.0 or more points among females and 0.6 points among males. Conclusions: During puberty, BMI is associated to biological and not chronological age.

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OBJECTIVE: We studied the prevalence of weight excess and short stature among school-age children in Chile over the past decade. METHODS: We designed a descriptive cross-sectional, school-based study to analyze nutritional and stature trends in prepubertal and pubertal boys and girls from 1986 to 1998. RESULTS: Between 1986 and 1998, we detected significant increases in obesity risk (body mass index between the 85th and 95th percentiles): from 8.3% to 19.6% in prepubertal males, from 5.4% to 14.6% in pubertal males, from 10.2% to 16.2% in prepubertal females, and from 9.7% to 24.9% in pubertal females. Obesity (body mass index > 95th percentile) increased significantly, from 4.3% to 29.5% in prepubertal males, from 1.6% to 14.6% in pubertal, from 4.7% to 24.0% in prepubertal females, and from 2.3% to 17.6% in pubertal females. During this same period, the prevalences of short stature (height for age below the 10th percentile) decreased from 40.9% to 12.0% in prepubertal males, from 44.2% to 20.4% in pubertal males, from 29.8% to 12.7% in prepubertal females, and from 41.1% to 25.8% in pubertal females. CONCLUSIONS: Chile represents a special model of fast changes in nutritional and growth trends due to social and political interventions and economic development. The significance of these findings in the health of Chilean adults and the urgency to implement measures to prevent further increases in obesity and simultaneously decrease the prevalence of short stature are discussed.

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Iodine deficiency has been a public health problem in most Latin American countries. Massive programs of salt iodization have achieved great progress toward its elimination but no consistent monitoring has been applied. We used the ThyroMobil model to visit 163 sites in 13 countries and assess randomly selected schoolchildren of both genders 6-12 years of age. The median urinary iodine concentration (8208 samples) varied from 72 to 540 microg/L. One national median was below the recommended range of 100-200 microg/L; five were 100-200 microg/L, and seven were higher than 200 microg/L, including three greter than 300 microg/L. Urinary iodine concentration correlated with the iodine content of salt in all countries. Median values of thyroid volume were within the normal range for age in all countries, but the goiter prevalence varied markedly from 3.1% to 25.0% because of scatter. The median iodine content of salt from local markets (2734 samples) varied from 5.9 parts per million (ppm) to 78 ppm and was greater than 15 ppm in 83.1% of all samples. Only seven countries had higher than 15 ppm iodine in 80% of the samples, and only three had greater than 15 ppm in at least 90%. Iodized salt was available at retail level in all countries but its median iodine content was within the recommended range (20-40 ppm) in only five. This study, the first to apply a standardized assessment strategy to recent iodine nutrition in Latin America, documents a remarkable success in the elimination of iodine deficiency by iodized salt in all but 1 of the 13 countries. Some iodine excess occurs, but side effects have not been reported so far, and two countries have already decreased their legal levels of salt iodization and improved the quality control of iodized salt, in part because of our results. The present work should be followed by regular monitoring of iodine nutrition and thyroid function, especially in the countries presently exposed to iodine excess.

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BACKGROUND: Body mass index (BMI) is the recommended parameter to assess the nutritional status of subjects aged less than 20 years. However, during puberty the correlation between BMI and fat mass decreases notably. Therefore, the use of BMI for the diagnosis of obesity during puberty may be misleading. AIM: To evaluate the variations of the BMI during puberty according to chronological and biological ages. MATERIAL AND METHODS: Descriptive cross sectional study in school age children of elementary and high schools (4,531 males and 5,326 females) representing all socioeconomic strata of 4 regions of Chile. BMI was calculated from weight and height measurements (W/H2) and pubertal development was evaluated according to Tanner stages. The sample selected to evaluate the variations of BMI according to chronological age and pubertal stages consisted in 3,913 females aged 8-14 years and 2,494 males aged 10-16 years. Analyses of variance (F test) and Tukey HSD test were used to compare mean BMI according to chronological and biological ages. RESULTS: The age of onset of puberty (Tanner Stages IB2 and G2) varied greatly, from 8 to 14 years in females and 10 to 16 years in males. Mean BMI in a specific stage of pubertal development did not show significant differences according to age in both sexes. However, there were significant differences (p < 0.05) in mean BMI when comparing children of the same chronological age but in different Tanner stages. Per each stage of Tanner development, BMI increased 1.0 or more points among females and 0.6 points among males. CONCLUSIONS: During puberty, BMI is associated to biological and not chronological age.

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BACKGROUND: In Chile, the recommendation for salt iodination was reduced from 100 to 40 ppm, after detecting high urinary iodine excretion in school age children. AIM: To assess iodine nutrition in school age children after the modification of salt iodination. SUBJECTS AND METHODS: Iodine nutrition was studied in 3712 school age Chilean children of primary level in 4 areas (Calama, Santiago, Temuco and Punta Arenas) through palpation of thyroid gland, urinary iodine excretion and iodine concentration in salt for human consumption of the surveyed areas. RESULTS: A 6.4% goiter prevalence was found (5.9% in boys and 6.8% in girls). Grade Ia goiter was more common (5.0%), without detecting differences between areas (7.3% in Calama, 5.9% in Santiago, 5.9 in Temuco and 6.7 in Punta Arenas). Iodine concentration in salt for human consumption of the areas was adequate according to the recent modification of Chilean legislation (25.4 mgI/g salt in Calama, 36.2 in Santiago, 27.7 in Temuco and 33.4 in Punta Arenas). Urinary iodine excretion was very high according to recommendation in boys and girls (2838 and 2852 mgI/g salt in Calama, 700 and 837 in Santiago, 1318 and 1438 in Temuco, 407 and 312 in Punta Arenas). CONCLUSIONS: Endemic goiter is not longer a problem in Chile. Salt iodination is in agreement with present legislation. However, urinary iodine excretion increased in Calama and Temuco, did not change in Santiago and decreased only in Punta Arenas in spite of the changes in the legislation. It is necessary to investigate the causes of the high urinary iodine excretions detected in school age children, and it is very important to have a continuous surveillance of iodine nutrition in Chile.

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