BES2003 Poster Presentations Thyroid (27 abstracts)
Serum TSH and thyroid autoantibodies in thyroidal and extrathyroidal disease
PPA Smyth 1 , D Kavanagh 2 , DF Smith 1 , CG Brennan 1 , F Fleming 2 , ADK Hill 2 , EWM Mc Dermott 2 , NJ O'Higgins 2 , P Barrett 3 , C Thompson 3 & MJ Moriarty 4
1Endocrine Laboratory, Department of Medicine and Therapeutics, University College Dublin, Republic of Ireland; 2Department of Surgery, University College Dublin and St Vincent's University Hospital,Dublin,RepublicofIreland;[3Department of Endocrinology, Beaumont Hospital, Dublin, Republic of Ireland; 4St Luke's Hospital, Dublin, Republic of Ireland.
The relationship between serum TSH and thyroid autoantibodies is frequently used to classify thyroid disease both overt and subclinical. Further debate has centred on the validity of the cutoff point for serum TSH elevation (generally between 4-5 mU/l) which it has been suggested is inappropriately high. The significance of the presence of thyroid autoantibodies (hereafter termed antibody positivity) in extrathyroidal disease is unclear but an increased prevalence has been reported in breast cancer. In this study thyroid autoantibodies and serum TSH were measured in thyroid disease, controls and in patients with breast and other diverse malignancies. Thyroid peroxidase antibodies (TPO.Ab) and thyroglobulin antibodies (Tg.Ab) were measured using highly sensitive radioimmunoassays. Antibody positivity defined as TPO.Ab > 2.0 kIU/l; Tg.Ab >3.0 kIU/l was 80.5 % and 76.0% in hyperthyroidism and hypothyroidism respectively. Examination of the relationship between serum TSH interval and thyroid antibody positivity in the different patient groups showed that antibody positivity was significantly greater in breast cancer than in the control or diverse cancer groups even when TSH was in the lower half of the reference range (0.6-2.0mU/ml; p<0.05) and this increased further (37.2%, p< 0.01) in the upper half (2.1-4.0mU/ml). Even more significant were the findings when TSH was > 4.0mU/l where antibody positivity was 76.3% in breast cancer, 50% in diverse cancers but 20% in controls. In fact antibody positivity at this serum TSH interval in the breast cancer group asymptomatic for thyroid disease was indistinguishable from patients with known thyroid disease (75.7%). The findings suggest an underlying thyroid autoimmunity in many cancer patients which is most strongly expressed in breast cancer and may on the basis of serum TSH be associated with subtle thyroid dysfunction.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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