碘致甲状腺功能减退症的流行病学对比研究

目的：研究不同碘摄入量人群的临床甲减和亚临床甲减患病率,方法：选择盘山,彰武和黄骅3个农村社区（分别为低碘,适碘和高碘地区（）,在入户问卷调查的基础上行采样调查,共问卷调查16287人,采样3761人,所有采样对象接受体格检查,,测定血清TSH,甲状腺过氧化的酶抗体（TPOAb),甲状腺球蛋白抗体（TGAb)和甲状腺球蛋白（TG）,测定尿碘浓度及进行甲状腺B超检查,TSH异常者测定FT4,FT3和TSH受体抗体（TRAb)。结果：盘山,彰武和黄骅社区成人尿碘水平分别为103．1ug/L,374.8ug/L和614.6ug/L,盘山,彰武和黄骅社区临床甲减患病率分别为0．27％,0．95％和2．05％, 临临床甲减的患病率分别为0．91％,2．90％,和5．96％,引起临床甲减的主要原因是自身免疫性甲状腺炎,亚临床甲减中三分之一患者甲状腺自身抗体阳性,结论：横断面的流行病学对比研究证实碘摄入量增加有可能导致甲状腺功能减退症患病率增加。     

Reference intervals of serum thyroid function tests in a previously iodine-deficient area.

AIM: We undertook the present study to establish reference data for serum thyroid function tests in a previously iodine-deficient area. METHODS: Data from 4298 individuals, 20-79 years of age were available for the present analysis. Thyroid function (thyrotropin [TSH], free triiodothyronine [FT(3)], and free thyroxine [FT(4)]) and serum autoantibodies to thyroperoxidase (anti-TPOAb) were evaluated from blood samples. Thyroid structure and size were measured by ultrasound. RESULTS: A reference population was selected comprising 1488 persons (825 men) by excluding subjects with known thyroid diseases, and with yet unknown thyroid disorders such as goitre, inhomogeneous thyroid pattern, nodules, hypoechogenicity and anti-TPOAb seropositivity. Reference intervals for serum TSH, FT(3), and FT(4) were 0.25-2.12 mIU/L, 3.8-7.0 pmol/L, and 8.3-18.9 pmol/L, respectively. Reference serum TSH levels were not comparable to the reference values that were recently established for the U.S. population and most reference values slightly differed from the reference values provided by the manufacturers. CONCLUSIONS: The reference ranges of thyroid function tests in this formerly iodine-deficient region are distinct from the reference ranges that were established in areas with iodine sufficiency. Creating a reference population in the present setting should include thyroid ultrasound in order to exclude yet undiagnosed thyroid disorders.     

Serum TSH, T(4), and thyroid antibodies in the United States population (1988 to 1994): National Health and Nutrition Examination Survey (NHANES III)

NHANES III measured serum TSH, total serum T(4), antithyroperoxidase (TPOAb), and antithyroglobulin (TgAb) antibodies from a sample of 17,353 people aged > or =12 yr representing the geographic and ethnic distribution of the U.S. population. These data provide a reference for other studies of these analytes in the U.S. For the 16,533 people who did not report thyroid disease, goiter, or taking thyroid medications (disease-free population), we determined mean concentrations of TSH, T(4), TgAb, and TPOAb. A reference population of 13,344 people was selected from the disease-free population by excluding, in addition, those who were pregnant, taking androgens or estrogens, who had thyroid antibodies, or biochemical hypothyroidism or hyperthyroidism. The influence of demographics on TSH, T(4), and antibodies was examined. Hypothyroidism was found in 4.6% of the U.S. population (0.3% clinical and 4.3% subclinical) and hyperthyroidism in 1.3% (0.5% clinical and 0.7% subclinical). (Subclinical hypothyroidism is used in this paper to mean mild hypothyroidism, the term now preferred by the American Thyroid Association for the laboratory findings described.) For the disease-free population, mean serum TSH was 1.50 (95% confidence interval, 1.46-1.54) mIU/liter, was higher in females than males, and higher in white non-Hispanics (whites) [1.57 (1.52-1.62) mIU/liter] than black non-Hispanics (blacks) [1.18 (1.14-1.21) mIU/liter] (P < 0.001) or Mexican Americans [1.43 (1.40-1.46) mIU/liter] (P < 0.001). TgAb were positive in 10.4 +/- 0.5% and TPOAb, in 11.3 +/- 0.4%; positive antibodies were more prevalent in women than men, increased with age, and TPOAb were less prevalent in blacks (4.5 +/- 0.3%) than in whites (12.3 +/- 0.5%) (P < 0.001). TPOAb were significantly associated with hypo or hyperthyroidism, but TgAb were not. Using the reference population, geometric mean TSH was 1.40 +/- 0.02 mIU/liter and increased with age, and was significantly lower in blacks (1.18 +/- 0.02 mIU/liter) than whites (1.45 +/- 0.02 mIU/liter) (P < 0.001) and Mexican Americans (1.37 +/- 0.02 mIU/liter) (P < 0.001). Arithmetic mean total T(4) was 112.3 +/- 0.7 nmol/liter in the disease-free population and was consistently higher among Mexican Americans in all populations. In the reference population, mean total T(4) in Mexican Americans was (116.3 +/- 0.7 nmol/liter), significantly higher than whites (110.0 +/- 0.8 nmol/liter) or blacks (109.4 +/- 0.8 nmol/liter) (P < 0.0001). The difference persisted in all age groups. In summary, TSH and the prevalence of antithyroid antibodies are greater in females, increase with age, and are greater in whites and Mexican Americans than in blacks. TgAb alone in the absence of TPOAb is not significantly associated with thyroid disease. The lower prevalence of thyroid antibodies and lower TSH concentrations in blacks need more research to relate these findings to clinical status. A large proportion of the U.S. population unknowingly have laboratory evidence of thyroid disease, which supports the usefulness of screening for early detection.     

妊娠早期甲状腺功能筛查策略的有效性分析

目的 获得妊娠早期甲状腺功能异常的患病率,进行妊娠早期甲状腺功能筛查策略的有效性分析.方法调查中国沈阳2 899名妊娠早期妇女(4～12周).通过问卷调查方法收集所有孕妇的背景资料,将孕妇分为高风险组与非高风险组.应用妊娠早期特异性甲状腺功能正常参考范围,获得妊娠早期甲状腺功能异常患病率.结果高风险组甲状腺功能减退症患病率明显高于非高风险组(16.3%对5.3%,RR=3.1,95%CI 2.4～4.0,P＜0.01).甲状腺过氧化物酶抗体(TPOAb)阳性(RR=4.7,95%CI3.6～6.0,P＜0.01),甲状腺疾病个人史(RR=3.2,95%CI 1.9～5.4,P＜0.01)均可显著增加甲状腺疾病患病的风险.高风险组甲状腺功能亢进症的患病率明显高于非高风险组(3.1%对1.4%,RR=2.2,95%CI 1.2～3.9,P=0.006).TPOAb阳性(RR=2.6,95%CI 1.3～5.0,P=0.007),甲状腺疾病个人史(RR=4.7,95%CI 1.7～12.5,P=0.006)均可显著增加甲状腺功能亢进发生的风险.高风险组与非高风险组间相比低T4血症患病率差异无统计学意义(0.9%对0.9%,x2=0.008,P=0.928).仅在高危孕妇中筛查甲状腺功能会漏掉56.7%甲状腺功能减退症(临床和亚临床)患者及64.7%甲状腺功能亢进症(临床和亚临床)患者.结论推荐对妊娠早期所有孕妇进行甲状腺功能的筛查.筛查指标应当包括TSH、FT4和TPOAb.     

河北某水源性高碘地区成人甲状腺疾病的流行病学调查

目的：调查水源性高碘地区－河北省黄骅市歧口村、高头村≥14岁人群甲状腺疾病的流行状况,方法：入户问卷调查4230人的基础上,采样调查1074人,所有采样调查对象均详细填与甲状腺疾病调查表,接受体检查和B超检查,测定血清促甲状腺激素（TSH）、甲状腺自身抗体（TAA）和甲状腺球蛋白（TG）,留取空腹尿样测量尿碘、TSH异常者测定甲状腺激素和TSH受体抗体（TRAb）。结果：采样人群的尿碘中位数为614．61μg/L。临床甲状腺功能亢进症（甲亢）和亚临床甲亢的患病率分别为1．21％和1．12％;临床甲亢中92．3％为Graves病所致,亚临床甲亢中75％TRAb阳性;回顾性分析普遍食盐碘化前后临床甲亢平均年发病率差异无显著性,临床甲状腺功能减低症（甲减）和亚临床甲减的患病率分别为1．96％和6．05％,患者TAA阳性率分别为85．71％和29．23％。采样人群甲状腺过氧化物酶抗体（TPOAb）和甲状腺球蛋白抗体（TGAb）阳性率分别为11．6％和9．3％。弥漫性甲状腺肿,结节性甲状腺肿、单发结节和多发结节的患病率分别为3．26％、2．61％、1．77％和6．4％。甲状腺癌病率为91．58／10万,结论：在尿磺中位数为614．61μg/L的碘营养状态下,甲状腺功能减退症和甲状腺癌患病率显著增高,提示这一碘摄入量并不安全。     

Thyroid Function Abnormalities and Cognitive Impairment in Elderly People: Results of the Invecchiare in Chianti Study

OBJECTIVES: To investigate thyroid function testing abnormalities in older persons and to explore the relationship between thyroid dysfunction and cognition.
DESIGN: Cross-sectional.
SETTING: Community-based.
PARTICIPANTS: One thousand one hundred seventy-one men and women aged 23 to 102.
MEASUREMENTS: Thyroid function was evaluated by measuring plasma concentrations of thyrotropin (TSH), free thyroxine (FT4), and free triiodothyronine (FT3). Cognition was evaluated using the Mini-Mental State Examination (MMSE). Prevalence of overt and subclinical thyroid dysfunction was evaluated in different age groups (<65 vs ≥65). Age trends in TSH, FT4, and FT3 were examined in euthyroid participants. The cross-sectional association between thyroid dysfunction and MMSE score was evaluated adjusting for confounders.
RESULTS: Subclinical hypothyroidism and subclinical hyperthyroidism were more prevalent in older than in younger participants (subclinical hypothyroidism, 3.5% vs 0.4%, P <.03; subclinical hyperthyroidism, 7.8% vs 1.9%, P <.002). In euthyroid participants, TSH and FT3 declined with age, whereas FT4 increased. Older participants with subclinical hyperthyroidism had lower MMSE scores than euthyroid subjects (22.61±6.88 vs 24.72±4.52, P <.03). In adjusted analyses, participants with subclinical hyperthyroidism were significantly more likely to have cognitive dysfunction (hazard rate=2.26, P =.003).
CONCLUSION: Subtle age-related changes in FT3, FT4, and TSH occur in individuals who remain euthyroid. Subclinical hyperthyroidism is the most prevalent thyroid dysfunction in Italian older persons and is associated with cognitive impairment.     

Comparative study of thyroid function and types of thyroid dysfunction in two areas in Denmark with slightly different iodine status

OBJECTIVE: The pattern of thyroid dysfunction seems to depend on the iodine status of the population. Prevalence of thyroid dysfunction could be a parameter to consider when evaluating iodine deficiency disorders in a population. DESIGN: Comparative cross-sectional investigation in two regions in Denmark with marginally different iodine excretion. METHODS: A random selection of 4649 participants from the Civil Registration System in Denmark in age groups between 18 and 65 years were examined. Thyroid dysfunction was evaluated from blood samples and questionnaires, and compared with results from ultrasonography. RESULTS: Median iodine excretion was 53 microg/l in Aalborg and 68 microg/l in Copenhagen. Previously diagnosed thyroid dysfunction was found with the same prevalence in the regions. Serum TSH was lower in Aalborg than in Copenhagen (P=0. 003) and declined with age in Aalborg, but not in Copenhagen. Not previously diagnosed hyperthyroidism was found with the same overall prevalence in the regions, but in age >40 years hyperthyroidism was more prevalent in Aalborg (1.3 vs 0.5%, P=0.017). Not previously diagnosed hypothyroidism was found more frequently in Aalborg (0.6 vs 0.2%, P=0.03). Hyperthyroidism was more often associated with macronodular thyroid structure at ultrasound in Aalborg and hypothyroidism was more often associated with patchy thyroid structure in Copenhagen. CONCLUSIONS: Significant differences in thyroid dysfunction were found between the regions with a minor difference in iodine excretion. The findings are in agreement with a higher prevalence of thyroid autonomy among the elderly in the most iodine-deficient region.     

Thyroid function in humans with morbid obesity.

Morbidly obese subjects may present with abnormal thyroid function tests but the reported data are scarce. Therefore, we studied the thyroid parameters in 144 morbidly obese patients, 110 females and 34 males, to assess the prevalence of hypothyroidism. Eleven percent (11.8%) carried the diagnosis of hypothyroidism and were undergoing levothyroxine (LT4) replacement therapy, 7.7% had newly diagnosed subclinical hypothyroidism, 0.7% had subclinical hyperthyroidism and 7.7% were euthyroid with positive antibodies (anti-thyroid peroxidase antibodies [TPOAb]). From the 144 subjects, we selected a cohort of 78 euthyroid subjects with negative TPOAb, who did not receive LT4 replacement or suppression therapy (the experimental group) and compared them to 77 normal-weight euthyroid subjects, TPOA-negative, matched for age and gender who served as controls. The experimental group had higher serum levels of triiodothyronine (T3), thyroxine (T4), free triiodothyronine (FT3), and thyrotropin (TSH) compared to the control group. Serum TSH concentration was associated with fasting serum insulin levels and insulin resistance but not with serum leptin levels, body mass index (BMI), fat mass, and lean body mass. In conclusion, in morbidly obese individuals, the prevalence of overt and subclinical hypothyroidism was high (19.5%). The morbidly obese subjects have higher levels of T3, FT3, T4, and TSH, probably the result of the reset of their central thyrostat at higher level.     

93例亚临床甲状腺功能减退症的随访研究

目的 研究不同碘摄入量地区亚临床甲状腺功能减退症(甲减)的流行病学特点和影响转归的因素。方法 选择盘山、彰武和黄骅3个农村社区(分别为低碘、适碘和高碘地区)，在入户调查的基础上行采样调查。测定血清TSH、甲状腺过氧化物酶抗体(TPOAb)、甲状腺球蛋白抗体(TGAb)、尿碘浓度及进行甲状腺B超检查，TSH异常者测定FT3、FT4，筛选出118例亚临床甲减患者。盘山和彰武社区于2年后、黄骅社区于1年后进行随访，再次进行以上检查。结果 盘山、彰武和黄骅社区亚临床甲减的患病率分别为0．73％、2．90％和5．96％。亚临床甲减的病因33．1％是自身免疫性甲状腺疾病。在随访到的93例亚临床甲减患者中有4例女性进展为临床甲减。结论 随着碘摄入量的增加亚临床甲减的患病率增加，但无明显性别差异。随访研究证实女性、甲状腺自身抗体阳性是亚临床甲减患者进展至临床甲减的危险因素，碘摄入量与亚临床甲减的转归无关。     

Chronic iodine excess does not increase the incidence of hyperthyroidism: a prospective community-based epidemiological survey in China

OBJECTIVE: An increasing incidence of hyperthyroidism has been observed when iodine supplementation has been introduced to an iodine-deficient population. Moreover, the influence of chronic more than adequate or excessive iodine intake on the epidemiological features of hyperthyroidism has not been widely and thoroughly described. To investigate the influences of different iodine intake levels on the incidence of hyperthyroidism, we conducted a prospective community-based survey in three communities with mild-deficient, more than adequate (previously mild deficient iodine intake), and excessive iodine intake. SUBJECTS AND METHODS: In three rural Chinese communities, a total of 3761 unselected inhabitants aged above 13 years participated in the original investigation and 3018 of them received identical examinations after 5 years. Thyroid function, levels of thyroid peroxidase antibody (TPOAb), thyroglobulin antibody and urinary iodine excretion were measured and thyroid ultrasound examination was also performed. RESULTS: In three communities, median urinary iodine excretion was 88, 214, and 634 microg/l (P<0.05) respectively. The cumulative incidence of hyperthyroidism was 1.4, 0.9, and 0.8% (P>0.05) respectively. Autoimmune hyperthyroidism was predominant in thyroid hyperfunction in all the three cohorts. Either positive TPOAb (>50 U/ml) or goiter in original healthy participants was associated with the occurrence of unsuspected hyperthyroidism in 5 years (logistic regression, OR=4.2 (95% CI 1.7-8.8) for positive TPOAb, OR=3.1 (95% CI 1.4-6.8) for goiter). CONCLUSION: Iodine supplementation may not induce an increase in hyperthyroidism in a previously mildly iodine-deficient population. Chronic iodine excess does not apparently increase the risk of autoimmune hyperthyroidism, suggesting that excessive iodine intake may not be an environmental factor involved in the occurrence of autoimmune hyperthyroidism.     

Investigations of thyroid hormones and antibodies based on a community health survey: the Busselton thyroid study

OBJECTIVE: Overt or subclinical thyroid dysfunction is common within the community, yet the significance of subtle anomalies in thyroid function tests remains contentious. The aims of this study were to: (a) establish reference intervals for serum-free thyroxine (FT4), thyroid-stimulating hormone (TSH) and thyroid antibodies (antithyroperoxidase, TPOAb and antithyroglobulin, TgAb) in the Busselton community of south-western Western Australia; and (b) determine the prevalence of thyroid hormone anomalies in this community. SUBJECTS AND DESIGN: In 1981, 2115 adults residing in Busselton participated in a cross-sectional health survey that involved blood collection and a questionnaire on lifestyle and general health history. MEASUREMENTS: Serum samples were analysed for FT4, TSH, TPOAb and TgAb by immunochemiluminescent assays. RESULTS: Based on standard statistical approaches and using guidelines recommended by the National Academy of Clinical Biochemistry (NACB), reference intervals were derived for each analyte: 9-23 pmol/l for FT4, 0.4-4.0 mIU/l (TSH), < 35 KIU/l (TPOAb) and < 55 KIU/l (TgAb). The prevalence of elevated thyroid antibodies was 12.4% among subjects without a history of thyroid disease and is more common in women than in men. Elevated thyroid antibody levels were observed at both extremes of TSH abnormality, but were more commonly increased when TSH levels were above 4.0 mIU/l (63% subjects) than for those with TSH levels 0.4-4.0 mIU/l (7.8% subjects). CONCLUSIONS: This study establishes the prevalence of antibodies to thyroperoxidase and thyroglobulin in a community-based sample and reference intervals for free T4 and TSH. When the NACB decision limits are applied to older men or women, there is a markedly increased number with 'elevated' autoantibody levels compared to sex- and age-specific reference intervals.     

Lower prevalence of mild hyperthyroidism related to a higher iodine intake in the population: prospective study of a mandatory iodization programme

Objective  Marked differences in pattern of thyroid dysfunction are seen in populations with different iodine intakes. We evaluated the influence of a higher iodine intake on thyroid hormone levels and the prevalence of thyroid dysfunction in the Danish population.
Design  Two cross-sectional studies matched on a group level according to sex and age.
Participants  In all, 8219 individuals were examined before ( n  = 4649) or after ( n  = 3570) the introduction of a mandatory iodization programme in 2000 in two regions with established mild and moderate iodine deficiency. Serum TSH, fT₄ and fT₃ were measured. An ultrasonography of the thyroid was performed.
Results  We found a higher median serum TSH after the introduction of mandatory iodization of salt: 1·51 mU/l (10–90th percentiles: 0·72–3·00) vs. 1·30 mU/l (10–90th percentiles: 0·59–2·66) before iodization. The difference was found in both regions and across age groups. There was a lower prevalence of mild hyperthyroidism and a tendency towards a lower prevalence of overt hyperthyroidism. The prevalence of mild hypothyroidism increased, most pronounced among young women after iodization. Conversely, there was a lower prevalence of undiagnosed overt hypothyroidism. However, when currently treated participants were included, the prevalence of hypothyroidism increased after iodization in the area with formerly mild iodine deficiency.
Conclusion  A change in pattern of thyroid dysfunction was seen in relation to mandatory iodization of salt. There was no rise in the prevalence of hyperthyroidism and the prevalence of mild hyperthyroidism was halved. Conversely, prevalence of hypothyroidism increased.     

High iodine intake is a risk factor of post-partum thyroiditis: result of a survey from Shenyang, China

The aim of the present study is to obtain the epidemiological data on post-partum thyroiditis (PPT) firstly in Chinese women, and to tryto evaluate whether excessive intake of iodine in post-partum women imposes any danger of occurring PPT. Sixty hundred and ten pregnant women were involved in the cohort just before delivery. Four hundred and eighty-eight (80%) of them accepted taking part in follow-ups more than 6 months post-partum. A blood sample was taken from participants before delivery and every 3 months post-partum for testing of serum TSH, thyroid autoantibodies. Free T3 (FT3), free T4 (FT4) and TSH receptor antibody (TRAb) were detected if TSH was abnormal. The iodine nutrition was evaluated according to the mean level of the fasting urinary iodine excretions at different times during the studying period, and participants were subgrouped into 3 categories with low, adequate and high iodine intake. For those participants who had thyroid dysfunction within 6 months post-partum, the follow-up persisted for 1 yr. Of 488 pregnant women, PPT developed in 11.9% (58/488). Given overt and subclinical PPT, the prevalence was 7.17% (no.=35) and 4.71% (no.=23), respectively. There was a strong association between the presence of thyroid peroxidase antibody (TPOAb) at delivery and the risk of developing PPT [RR=6.76, 95% (CI) 4.42-10.34]. Overt cases had much higher titers of TPOAb than subclinical patients (all p<0.05). The median urinary iodine (MUI) of patients with PPT was significantly higher than that of healthy women (231.93 vs 199.88 microg/l p=0.00153). Both the prevalence of PPT and positive TPOAb rise with the increment of iodine intakes. Pregnant women with high iodine intake had more risk of developing PPT when compared with those with low iodine intake (RR=2.92, 95%CI 1.31-6.50). We concluded that positive TPOAb was of value for predicting the occurrence and severity of PPT, and a high iodine intake was a risk factor triggering PPT.     

The spectrum of thyroid disorders in an iodine-deficient community: the Pescopagano survey

We carefully assessed thyroid status and goiter by ultrasound in 1411 subjects virtually representing the entire resident population of Pescopagano, an iodine-deficient village of Southern Italy. Median urinary iodine excretion was 55 microg/L. The prevalence of goiter was 16.0% in children and 59.8% in adults. Thyroid nodularity was 0.5% in children and progressively increased with age to 28.5% in the 56- to 65-yr-old group. The prevalence of present or past hyperthyroidism was 2.9%, including 9 cases with toxic diffuse goiter and 20 with toxic nodular goiter. Functional autonomy was rare in children, progressively increased with age up to 15.4% in the elderly, and was related to nodular goiter. The prevalences of overt and subclinical hypothyroidism in the adults were 0.2% and 3.8%, respectively. Serum autoantibodies to thyroglobulin and thyroperoxidase were detected in 12.6% of the entire population. The prevalence of diffuse autoimmune thyroiditis was 3.5%, being very low in children. Thyroid cancer was found in only 1 case. In conclusion, in the present survey of an iodine-deficient community, a progressive increase with age of goiter prevalence, thyroid nodularity, and functional autonomy was observed. Hyperthyroidism was twice as high as that reported in iodine-sufficient areas, mainly due to an increased frequency of toxic nodular goiter. Although low titer serum thyroid antibodies were relatively frequent, the prevalences of both overt and subclinical autoimmune hypothyroidism were not different from those observed in iodine-sufficient areas.     

A population study of the association between thyroid autoantibodies in serum and abnormalities in thyroid function and structure

OBJECTIVE: Patients with autoimmune overt hypothyroidism may present with goitrous Hashimoto's disease or autoimmune atrophic thyroiditis. Little is known about the prevalence of subclinical autoimmune hypothyroidism. The aims of this study were to evaluate the association between thyroid autoantibodies in serum and abnormalities in thyroid function and structure, and to study the thyroid volume in subjects with subclinical autoimmune hypothyroidism. DESIGN: A population study including 4649 randomly selected subjects. MEASUREMENTS: Blood tests were used to analyse for thyroid peroxidase autoantibodies (TPO-Ab), thyroglobulin autoantibodies (Tg-Ab), TSH, fT3 and fT4. RESULTS: Thyroid volume was categorized as small (< 6.6 ml) in 4.7%, normal (6.6-14.9 ml) in 60.4% and large (> 14.9 ml) in 34.9% of participants. Thyroid nodules were found in 29.7%. Serum TSH was low (< 0.4 mIU/l) in 4.7%, normal (0.4-3.6) in 91.0% and high (> 3.6) in 4.3%. The prevalence rate of subclinical goitrous Hashimoto's disease was 0.62% and of subclinical autoimmune atrophic thyroiditis 0.24%. There was a strong association between large volume and autoantibodies, but only in subjects with elevated TSH (P < 0.001). An association between thyroid nodules and TPO-Ab in univariate analyses (P < 0.001) was due to confounding by sex and age (multivariate model, P = 0.23). CONCLUSION: We identified a subgroup of the population with subclinical goitrous Hashimoto's disease and a smaller subgroup with subclinical autoimmune atrophic thyroiditis. This relationship between small and large thyroid volume in subclinical disease is opposite to that in overt disease, which may suggest that the period between development of a small volume with circulating autoantibodies and overt hypothyroidism is relatively short.     

Five‐year incidence and progression of thyroid dysfunction in an older population

Background: Very few studies have assessed both the incidence and progression of thyroid dysfunction in a single older population‐based cohort. In this study, we aimed to assess the 5‐year incidence, progression and risk factors for development of thyroid dysfunction in an older Australian population. Methods: The Blue Mountains Eye Study is a longitudinal population‐based cohort study. During 1997–1999, 1768 participants (≥55 years) had thyroid function assessed. After excluding participants reporting any form of treatment for their thyroid condition at baseline, 951 participants (91.4%) without thyroid dysfunction and 54 (5.4%) with thyroid dysfunction were re‐examined 5 years later. Thyroid dysfunction was defined using serum thyrotropin (thyroid stimulating hormone (TSH)) screen, followed by serum free T4 assessment. Results: The overall 5‐year incidence of thyroid dysfunction was 4.7% (95% confidence interval (CI) 3.4–6.1). Obesity (body mass index ≥ 30 kg/m²) and serum TSH > 2 mIU/L at baseline predicted incident overt hypothyroidism (odds ratio (OR) 4.05, CI 1.74–9.41) and (OR 5.46, CI 1.16–25.67) respectively. The 5‐year incidence of subclinical hypothyroidism was significantly higher in women than in men, 2.5% versus 0.7% (P= 0.03). Progression to overt hypothyroidism was observed in 17.9% of subjects with subclinical hypothyroidism over 5 years. Conclusions: The 5‐year incidence of thyroid dysfunction in this older population was relatively low, and was associated with obesity and serum TSH level > 2 mIU/L at baseline. Over one in six persons with subclinical hypothyroidism progressed to overt thyroid dysfunction over the 5‐year period. Our findings highlight the need for appropriate management of subclinical hypothyroidism among older people.     

Alterations in thyroid function tests in aged hospitalized patients: prevalence, aetiology and clinical outcome

Background Thyroid dysfunction is common in aged people and has recently been associated to mortality. Aims Our aims have been (1) to assess the prevalence of alterations in thyroid function tests in hospitalized patients over age 60 years and (2) to study the relationship between thyroid functional status and mortality during hospitalization. Methods We studied a group of 447 patients (62% women), aged 61–101 year, hospitalized during 2005. Thyroid dysfunction was assessed by measuring serum concentrations of thyrotrophin (TSH), free thyroxine (FT4), and free thriiodothyronine (FT3). Thyroid autoimmune status was evaluated through thyroid peroxidase (TPO) and thyroglobulin (TG) antibodies quantification. Results Twenty‐one patients (4·7%, 19 women) showed previously known thyroid dysfunction. 332 patients (74·3%) showed alterations in thyroid function tests. Euthyroid sick syndrome (ESS) was the derangement more frequently found (n = 278, 62·2%). After excluding ESS patients, 60 patients (13·4%) showed thyroid dysfunction: overt hypothyroidism, 14 (3·1%); subclinical hypothyroidism, 25 (5·6%); overt hyperthyroidism, 11 (2·5%), and subclinical hyperthyroidism, 10 patients (2·2%). Thyroid autoimmunity was positive in only 4·0% and 2·3% of patients, for TPOAb and TgAb, respectively. The presence of alterations in thyroid function tests was positively associated with the age of the patients and mortality during hospital stay (P < 0·001). Serum levels of FT3 were negatively related to death during hospitalization (OR 0·56; CI 95%, 0·38–0·81; P < 0·01). Conclusions About three quarters of patients admitted in our geriatric unit exhibited alterations in thyroid function tests. This finding was associated with elevated age and poor prognosis. The reduction of FT3 values was a powerful predictor for mortality during hospitalization in elderly patients.     

Tobacco smoking and thyroid function: a population-based study

BACKGROUND: The association between tobacco smoking and thyroid function is incompletely understood. METHODS: In a cross-sectional, population-based study conducted between August 15, 1995, and June 18, 1997, of 20 479 women and 10 355 men without previously known thyroid disease, we calculated the geometric mean serum concentration of thyrotropin and the prevalence of hypothyroidism and hyperthyroidism among current, former, and never smokers. RESULTS: Among women, the mean thyrotropin level was lower in current (1.33 mIU/L; 95% confidence interval [CI], 1.29-1.36 mIU/L) and former smokers (1.61 mIU/L; 95% CI, 1.56-1.65 mIU/L) compared with never smokers (1.66 mIU/L; 95% CI, 1.63-1.70 mIU/L). Similarly, among men, the mean thyrotropin level was lower in current (1.40 mIU/L; 95% CI, 1.36-1.44 mIU/L) and former smokers (1.61 mIU/L; 95% CI, 1.57-1.66 mIU/L) compared with never smokers (1.70 mIU/L; 95% CI, 1.66-1.75 mIU/L). In former smokers, thyrotropin levels increased gradually with time since smoking cessation (P for trend < .001). Among current smokers, moderate daily smoking was associated with higher thyrotropin levels than heavier smoking. In women, the prevalence of overt hypothyroidism was lower in current smokers compared with never smokers (odds ratio, 0.60; 95% CI, 0.38-0.95), whereas the prevalence of overt hyperthyroidism was higher among current smokers (odds ratio, 2.37; 95% CI, 1.34-4.20). The associations related to subclinical thyroid dysfunction were similar to those for overt thyroid disease. CONCLUSIONS: These findings indicate that smoking is negatively associated with hypothyroidism but positively associated with hyperthyroidism. The associations with smoking cessation suggest that smoking may have reversible effects on thyroid function. Notably, we report for the first time, to our knowledge, a lower prevalence of overt hypothyroidism among current smokers.     

Low serum thyrotropin is associated with high plasma fibrinogen

BACKGROUND: Elevated plasma fibrinogen levels are associated with an increased risk of cardiovascular events. Decreased serum TSH predicts vascular mortality, which hypothetically could be explained in part by alterations in the blood coagulation system. OBJECTIVE: The objective of this study was to investigate the association between thyroid function and plasma fibrinogen levels in a general population. DESIGN: The population-based Study of Health in Pomerania was performed in a previously iodine-deficient area in Germany, including 4310 subjects, aged 20-79 yr. Data for 3804 individuals without thyroid disease were analyzed. Analysis revealed an association between thyroid function status and plasma fibrinogen concentration. RESULTS: Elevated fibrinogen levels (>3.25 g/liter) were observed in 14 subjects with increased serum TSH levels (32.6%), 973 euthyroid subjects (28.9%), 158 subjects with decreased serum TSH levels (40.7%), and six individuals with overt hyperthyroidism (54.4%). Logistic regression analysis revealed decreased serum TSH as an independent risk factor for elevated fibrinogen levels (odds ratio, 1.42; 95% confidence interval, 1.12-1.80). CONCLUSIONS: Thyroid function is associated with plasma fibrinogen. Decreased serum TSH is an independent risk factor for elevated plasma fibrinogen levels as a possible explanation for the high cardiovascular mortality among affected subjects.