***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: BACKGROUND Race/ethnicity may be a newly recognized risk factor for Graves ' disease . OBJECTIVE The aim of this study was to examine the prevalence of thyrotoxicosis by race/ethnicity in Americans aged 12 - 49 years using three National Health and Nutritional Examination Surveys ( NHANES ) . METHODS Data were analyzed from 17,939 participants in NHANES III ( 1988 - 1994 ) , NHANES 1999 - 2002 , and NHANES 2007 - 2010 with available thyroid function test results . Thyrotoxicosis was defined as a serum thyrotropin ( TSH ) of ≤0.1 mIU/L or subjects taking methimazole or propylthiouracil , and overt thyrotoxicosis was defined as high serum thyroxine and a serum TSH of ≤0.1 mIU/L. Logistic regression was performed accounting for the complex sampling design of NHANES , and the results from all three NHANES surveys were combined using a r and om-effects model . RESULTS There were 75 study participants with point prevalent thyrotoxicosis  , representing a pooled prevalence of 0.4 % for Americans aged 12 - 49 years . Prevalent thyrotoxicosis was nearly three times more likely in non-Hispanic black subjects compared with non-Hispanic whites ( OR=2.9 [ CI 1.5 - 5.7 ] ) , while there was no difference between the prevalence of thyrotoxicosis in Mexican Americans compared to non-Hispanic whites ( OR=1.2 [ CI 0.6 - 2.4 ] ; I2 for heterogeneity=0 % for both ) . Among 27 patients with overt thyrotoxicosis  , the odds ratio was 8.7 [ CI 0.7 - 112.6 ] for non-Hispanic blacks and 4.6 [ CI 0.4 - 59.3 ] for Mexican Americans compared with non-Hispanic whites . CONCLUSIONS The results suggest there are race/ethnicity differences in the prevalence of thyrotoxicosis . Future studies should address whether these differences are due to heritable factors , environmental exposures , or a combination of both Background : Despite the high prevalence of thyroid dysfunction , the epidemiology and natural course of these disorders have not been identified yet . Aim : The present survey was conducted to determine the incidence of thyroid dysfunction and natural course of sub clinical thyroid disorders in an urban community of Tehran , I.R. Iran . Subjects and methods :  Serum TSH and thyroperoxidase antibody ( TPOAb )  were measured at baseline and after 6.7 yr from a sample of 1999 r and omly selected subjects aged ≥20 yr , participants of the Tehran Lipid and Glucose Study ( TLGS ) . Median TSH value and 2.5 , 5 , 95 , and 97.5 TSH percentiles were determined at baseline using data obtained from 808 negative TPOAb subjects with no history of any thyroid disease or surgery , goiter , nodule , taking thyroid hormone preparations or anti-thyroid drugs . In those with abnormal TSH level , total T4 and T3 uptake were measured and free T4 index was calculated . Results : Normal TSH reference range was 0.4–5.8 µU/ml according to the 2.5 and 97.5 TSH percentiles . The incidence rates of thyroid function abnormalities in 1000 subjects per year were as follows : clinical hypothyroidism : 0.28 in women and 0.21 in men ; sub clinical hypothyroidism : 11.59 in women and 4.69 in men ; clinical hyperthyroidism : 1.4 in women and 0.21 in men ; and sub clinical hyperthyroidism : 5.72 in women and 3.62 in men . A significant increase was found in the frequency of positive TPOAb in women from 15.9 to 17.7 % ( p=0.006 ) . Of 8 women with sub clinical hypothyroidism at baseline , 5 remained unchanged , 1 became normal , and 1 developed clinical hypothyroidism at follow-up . Two women with sub clinical hyperthyroidism normalized at follow-up . Of 2 men with sub clinical hypothyroidism at baseline , 1 remained unchanged , whereas the other progressed to clinical hypothyroidism . Conclusion : After a 6.7 yr follow-up significant increase in the incidence of sub clinical thyroid disorders was observed in both men and women , as compared to overt thyroid dysfunction . Increase in the prevalence of TPOAb positivity was observed only in women BACKGROUND AND OBJECTIVE The original Whlckham Survey documented the prevalence of thyroid disorders in a r and omly selected sample of 2779 adults which matched the population of Great Britain in age , sex and social class . The aim of the twenty‐year follow‐up survey was to determine the Incidence and natural history of thyroid disease in this cohort We evaluated the prevalence of autoimmune thyroiditis in a r and om sample of 1188 schoolchildren aged 8 - 13 years with normalized iodine intake in the Islamic Republic of Iran . The prevalence of goitre was 39.6 % ; the majority had palpable but non-visible goitre . Of a sub sample of 500 children , median urinary iodine excretion ( 18/8 microg/dL ) indicated normal iodine intake . Thyroid peroxidase ( TPO ) antibody was positive in 3.7 % of children and was significantly correlated with the prevalence of goitre and hypothyroidism . No correlation was seen between urinary iodine excretion and positive TPO antibody , mean TPO antibody , hypothyroidism or prevalence of goitre . Autoimmune thyroiditis explains some cases of goitre but other goitrogenic factors need to be evaluated As the production , distribution and consumption of iodized salt has increased in recent years , this study was carried out to assess iodine status in Tehran in 1996 . 1146 families comprising 5140 subjects in the twenty districts of Tehran city from all age groups were r and omly selected . Thyroid size was examined by palpation and grade d according to the WHO classification . In 163 families selected r and omly , thyroid size was determined by ultrasonography and urinary iodine was measured by digestion method .  Serum T4 , T3 and TSH ( IRMA ) concentrations were also assayed by kits . Percentage of grade s 1 & 2 goiter were 44 & 44 % in females and 49 & 33 % in males respectively . Median urinary iodine was 17.5 micrograms/dl . Mean serum T4 , T3 and TSH were 8.41 + /- 1.4 micrograms/dl , 170 + /- 37 ng/dl and 1.4 + /- 0.8 mu/ml , respectively . In 118 children aged 6 - 10 years median urinary iodine was 17.5 micrograms/dl . Thyroid volume in children was 4.3 + /- 1.9 ml . No correlation was established between the thyroid volume and goiter grade . This study points to the adequacy of  iodine  intake in the majority of families residing in Tehran The occurrence of iodine-induced hyperthyroidism ( IIH ) has been reported after iodine supplementation from clinics and hospitals , but not following an epidemiologic survey . We studied the prevalence of thyroid derangement in a population following iodine supplementation . One yr after more than 75 % of the population had been consuming 40 ppm iodized salt ; information regarding history of endemic goiter and iodized salt production , distribution , consumption and monitoring were collected in four cities of the Islamic Republic of Iran . A total of 6048 subjects were r and omly selected . All subjects were assessed for size of goiter , and urinary iodine and serum T4 , T3 , TSH , anti-thyroglobulin and antithyroperoxide were measured . Before iodine supplementation , all four cities were areas of endemic goiter . The rate of household consumption of iodized salt was 50 , 75 and 90 % in 1994 , 1995 and 1996 , respectively . Ninety-one percent of the salt sample s contained 15–55 ppm iodide . Total goiter rate was 57 , 62 and 68 % ; median urinary iodine was 188 , 197 and 190 μg/l in the age groups of 6–18 , 19–40 and > 40 yr , respectively . Prevalence of clinical and sub clinical hyperthyroidism was 0.34 and 0.41 and those of clinical and sub clinical hypothyroidism were 0.51 and 1.07 % , respectively . Nine point eight and 18 % in the 19–40 yr age group and 17.6 and 25.6 % in > 40 yr old subjects had positive anti-thyroperoxidase and antithyroglobulin , respectively . This systemic epidemiologic study in an iodine deficient population showed that , following a well-executed iodine supplementation program , the occurrence of IIH is rare OBJECTIVE In a previous study in 1983 , goiter was found to be endemic in Shahriar , Iran .  Iodized salt has been distributed in the region for the past 12 years , and the present study was performed to examine the effect of iodide supplementation on indicators of iodine deficiency ( IDD ) and thyroid antibodies . DESIGN & METHODS A total of 3164 people , 58 % women and 42 % men , were selected by r and om sampling from the Shahriar area . Goiter was staged according to World Health Organization guidelines . Urinary iodine was measured by a digestion method , and thyroid hormone measurements were done by radioimmunoassay . The results were compared with those of 1983 . RESULTS Goiter prevalence before and after iodine supplementation was 50 and 40 % in men , 70 and 51 % in women , and 60 and 47 % in the whole community , respectively ( p < 0.001 ) . A decrease in the prevalence of goiter was observed especially in younger individuals . The mean urinary iodine excretion was 7.6 and 18.5 micrograms/dL , before and after iodine supplementation . In 1983 , the urinary iodine in 47.5 % of the population studied was between 2 to 5 micrograms/dL , while in 1995 , 65 % of the population studied had urinary iodine between 10 to 25 micrograms/dL , 12 years after iodine supplementation . Mean serum T4 , T3 , and thyroid-stimulating hormone ( TSH ) were normal before and after intervention . There was no significant change in occurrence of positive antibodies , or of hypo- and hyperthyroidism , following iodine supplementation . CONCLUSION The result of this study shows that the use of iodized salt causes an increase in excreted urinary iodine and a decrease in the prevalence of thyroid goiter , especially in younger age groups . Consumption of iodized salt with 40 parts per million ( ppm ) iodine has not caused increased prevalence of thyroid dysfunction in this area BACKGROUND Current guidelines used for establishing reference intervals for thyroid peroxidase antibodies ( TPOAb ) , recommended by the National Academy of Clinical Biochemistry , have been a matter of controversy . The present study sought to determine TPOAb reference intervals for different age and sex groups , as well as the TPOAb cutoff points for sub clinical and overt hypothyroidism in an iodine-sufficient population . METHODS This cross-sectional study was conducted within the framework of the prospect i ve Tehran Thyroid Study ( TTS ) , in which 4174 healthy euthyroid individuals were followed for 10 years .  Thyroid function tests and TPOAb  were assessed . RESULTS The mean age ± st and ard deviation of participants was 39.3 ± 15.2 years .  Estimated reference intervals for TPOAb corresponding to the 2.5th and 97.5th percentiles were 1.5 - 32.8 and 2.1 - 35 IU/mL in males and females , respectively . There were no significant variations in the different age groups in either sex . The optimal cutoff points for TPOAb were 18.38 and 14.77 IU/mL for predicting clinical and sub clinical hypothyroidism , respectively . CONCLUSIONS This study establishes the reference intervals and the optimal cutoff points for TPOAb in an iodine-sufficient population 
    Output:
    
Conclusions This is the first systematic review and meta- analysis , which investigated the epidemiology of hyperthyroidism in Iran .
It seems that the prevalence and incidence of hyperthyroidism among the general population in Iran is similar to that in other parts of the world