Blog
About

  • Record: found
  • Abstract: found
  • Article: not found

Subclinical Hypothyroidism after Radioiodine Exposure: Ukrainian–American Cohort Study of Thyroid Cancer and Other Thyroid Diseases after the Chornobyl Accident (1998–2000)

Read this article at

ScienceOpenPublisherPMC
Bookmark
      There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

      Abstract

      Background

      Hypothyroidism is the most common thyroid abnormality in patients treated with high doses of iodine-131 ( 131I). Data on risk of hypothyroidism from low to moderate 131I thyroid doses are limited and inconsistent.

      Objective

      This study was conducted to quantify the risk of hypothyroidism prevalence in relation to 131I doses received because of the Chornobyl accident.

      Methods

      This is a cross-sectional (1998–2000) screening study of thyroid diseases in a cohort of 11,853 individuals < 18 years of age at the time of the accident, with individual thyroid radioactivity measurements taken within 2 months of the accident. We measured thyroid-stimulating hormone (TSH), free thyroxine, and antibodies to thyroid peroxidase (ATPO) in serum.

      Results

      Mean age at examination of the analysis cohort was 21.6 years (range, 12.2–32.5 years), with 49% females. Mean 131I thyroid dose was 0.79 Gy (range, 0–40.7 Gy). There were 719 cases with hypothyroidism (TSH > 4 mIU/L), including 14 with overt hypothyroidism. We found a significant, small association between 131I thyroid doses and prevalent hypothyroidism, with the excess odds ratio (EOR) per gray of 0.10 (95% confidence interval, 0.03–0.21). EOR per gray was higher in individuals with ATPO ≤ 60 U/mL compared with individuals with ATPO > 60 U/mL ( p < 0.001).

      Conclusions

      This is the first study to find a significant relationship between prevalence of hypothyroidism and individual 131I thyroid doses due to environmental exposure. The radiation increase in hypothyroidism was small (10% per Gy) and limited largely to subclinical hypothyroidism. Prospective data are needed to evaluate the dynamics of radiation-related hypothyroidism and clarify the role of antithyroid antibodies.

      Related collections

      Most cited references 54

      • Record: found
      • Abstract: found
      • Article: not found

      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.
        Bookmark
        • Record: found
        • Abstract: found
        • Article: not found

        Subclinical thyroid disease: scientific review and guidelines for diagnosis and management.

        Patients with serum thyroid-stimulating hormone (TSH) levels outside the reference range and levels of free thyroxine (FT4) and triiodothyronine (T3) within the reference range are common in clinical practice. The necessity for further evaluation, possible treatment, and the urgency of treatment have not been clearly established. To define subclinical thyroid disease, review its epidemiology, recommend an appropriate evaluation, explore the risks and benefits of treatment and consequences of nontreatment, and determine whether population-based screening is warranted. MEDLINE, EMBASE, Biosis, the Agency for Healthcare Research and Quality, National Guideline Clearing House, the Cochrane Database of Systematic Reviews and Controlled Trials Register, and several National Health Services (UK) databases were searched for articles on subclinical thyroid disease published between 1995 and 2002. Articles published before 1995 were recommended by expert consultants. A total of 195 English-language or translated papers were reviewed. Editorials, individual case studies, studies enrolling fewer than 10 patients, and nonsystematic reviews were excluded. Information related to authorship, year of publication, number of subjects, study design, and results were extracted and formed the basis for an evidence report, consisting of tables and summaries of each subject area. The strength of the evidence that untreated subclinical thyroid disease is associated with clinical symptoms and adverse clinical outcomes was assessed and recommendations for clinical practice developed. Data relating the progression of subclinical to overt hypothyroidism were rated as good, but data relating treatment to prevention of progression were inadequate to determine a treatment benefit. Data relating a serum TSH level higher than 10 mIU/L to elevations in serum cholesterol were rated as fair but data relating to benefits of treatment were rated as insufficient. All other associations of symptoms and benefit of treatment were rated as insufficient or absent. Data relating a serum TSH concentration lower than 0.1 mIU/L to the presence of atrial fibrillation and progression to overt hyperthyroidism were rated as good, but no data supported treatment to prevent these outcomes. Data relating restoration of the TSH level to within the reference range with improvements in bone mineral density were rated as fair. Data addressing all other associations of subclinical hyperthyroid disease and adverse clinical outcomes or treatment benefits were rated as insufficient or absent. Subclinical hypothyroid disease in pregnancy is a special case and aggressive case finding and treatment in pregnant women can be justified. Data supporting associations of subclinical thyroid disease with symptoms or adverse clinical outcomes or benefits of treatment are few. The consequences of subclinical thyroid disease (serum TSH 0.1-0.45 mIU/L or 4.5-10.0 mIU/L) are minimal and we recommend against routine treatment of patients with TSH levels in these ranges. There is insufficient evidence to support population-based screening. Aggressive case finding is appropriate in pregnant women, women older than 60 years, and others at high risk for thyroid dysfunction.
          Bookmark
          • Record: found
          • Abstract: found
          • Article: not found

          The incidence of thyroid disorders in the community: a twenty-year follow-up of the Whickham Survey.

          The original Whickham Survey documented the prevalence of thyroid disorders in a randomly 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. Subjects were traced at follow-up via the Electoral Register, General Practice registers, Gateshead Family Health Services Authority register and Office of Population Censuses and Surveys. Eight hundred and twenty-five subjects (30% of the sample) had died and, in addition to death certificates, two-thirds had information from either hospital/General Practitioner notes or post-mortem reports to document morbidity prior to death. Of the 1877 known survivors, 96% participated in the follow-up study and 91% were tested for clinical, biochemical and immunological evidence of thyroid dysfunction. Outcomes in terms of morbidity and mortality were determined for over 97% of the original sample. The mean incidence (with 95% confidence intervals) of spontaneous hypothyroidism in women was 3.5/1000 survivors/year (2.8-4.5) rising to 4.1/1000 survivors/year (3.3-5.0) for all causes of hypothyroidism and in men was 0.6/1000 survivors/year (0.3-1.2). The mean incidence of hyperthyroidism in women was 0.8/1000 survivors/year (0.5-1.4) and was negligible in men. Similar incidence rates were calculated for the deceased subjects. An estimate of the probability of the development of hypothyroidism and hyperthyroidism at a particular time, i.e. the hazard rate, showed an increase with age in hypothyroidism but no age relation in hyperthyroidism. The frequency of goitre decreased with age with 10% of women and 2% of men having a goitre at follow-up, as compared to 23% and 5% in the same subjects respectively at the first survey. The presence of a goitre at either survey was not associated with any clinical or biochemical evidence of thyroid dysfunction. In women, an association was found between the development of a goitre and thyroid-antibody status at follow-up, but not initially. The risk of having developed hypothyroidism at follow-up was examined with respect to risk factors identified at first survey. The odds ratios (with 95% confidence intervals) of developing hypothyroidism with (a) raised serum TSH alone were 8 (3-20) for women and 44 (19-104) for men; (b) positive anti-thyroid antibodies alone were 8 (5-15) for women and 25 (10-63) for men; (c) both raised serum TSH and positive anti-thyroid antibodies were 38 (22-65) for women and 173 (81-370) for men. A logit model indicated that increasing values of serum TSH above 2mU/l at first survey increased the probability of developing hypothyroidism which was further increased in the presence of anti-thyroid antibodies. Neither a positive family history of any form of thyroid disease nor parity of women at first survey was associated with increased risk of developing hypothyroidism. Fasting cholesterol and triglyceride levels at first survey when corrected for age showed no association with the development of hypothyroidism in women. This historical cohort study has provided incidence data for thyroid disease over a twenty-year period for a representative cross-sectional sample of the population, and has allowed the determination of the importance of prognostic risk factors for thyroid disease identified twenty years earlier.
            Bookmark

            Author and article information

            Affiliations
            [1 ]Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland, USA;
            [2 ]Institute of Endocrinology and Metabolism, Kyiv, Ukraine;
            [3 ]Department of Medicine, The Thyroid Clinic, College of Physicians and Surgeons, Columbia University, New York, New York, USA;
            [4 ]Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland, USA;
            [5 ]Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York, USA;
            [6 ]Scientific Center for Radiation Medicine, Academy of Medical Science, Kyiv, Ukraine
            Author notes
            Address correspondence to A. Brenner, Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, MS 7238, 6120 Executive Blvd., Bethesda, MD 20892-7238 USA. Telephone: (301) 402-8680. Fax: (301) 402-0207. E-mail: brennera@ 123456mail.nih.gov

            The authors declare they have no competing financial interests.

            Journal
            Environ Health Perspect
            Environmental Health Perspectives
            National Institute of Environmental Health Sciences
            0091-6765
            1552-9924
            May 2009
            15 December 2008
            : 117
            : 5
            : 745-750
            2685836
            19479016
            10.1289/ehp.0800184
            ehp-117-745
            This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original DOI.
            Categories
            Research

            Comments

            Comment on this article