Clinical Endocrinology

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

Authors

  • Peter C. O'Leary,

    Corresponding author
    1. Clinical Biochemistry, Women's and Children's Health Service,
    2. The University of Western Australia, Schools of Women's and Infants’ Health, Medicine and Pharmacology and Population Health,
      Dr Peter O’Leary, Clinical Biochemistry Department, Women's and Children's Health Service, Princess Margaret Hospital, Roberts Rd, Subiaco WA., Australia. Tel.: +618 9323 6628; Fax: +618 9323 6611; E-mail: peter.oleary@health.wa.gov.au
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  • Peter H. Feddema,

    1. BioMediq-DPC, Melbourne,
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  • Valdo P. Michelangeli,

    1. BioMediq-DPC, Melbourne,
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  • Peter J. Leedman,

    1. The University of Western Australia, Schools of Women's and Infants’ Health, Medicine and Pharmacology and Population Health,
    2. Department of Endocrinology and Diabetes, Royal Perth Hospital,
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  • Gerard T. Chew,

    1. Department of Endocrinology and Diabetes, Royal Perth Hospital,
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  • Matthew Knuiman,

    1. The University of Western Australia, Schools of Women's and Infants’ Health, Medicine and Pharmacology and Population Health,
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  • Joey Kaye,

    1. Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Western Australia, Australia
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  • John P. Walsh

    1. Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Western Australia, Australia
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Dr Peter O’Leary, Clinical Biochemistry Department, Women's and Children's Health Service, Princess Margaret Hospital, Roberts Rd, Subiaco WA., Australia. Tel.: +618 9323 6628; Fax: +618 9323 6611; E-mail: peter.oleary@health.wa.gov.au

Summary

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 0·4–4·0mIU/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.

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