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SMYTH
Thyroglobulin autoantibodies in iodized subjects: relationship between epitope specificities and longitudinal antibody activity.Okosieme OE, Premawardhana LD, Jayasinghe A, Kaluarachi WN, Parkes AB, Smyth PP, Lejeune PJ, Ruf J, Lazarus JH. Thyroid. 2005 Sep;15(9):1067-72. [abstract only]
"INTRODUCTION: We previously reported a high thyroglobulin autoantibodies (TgAb) prevalence in healthy Sri Lankans after iodine supplementation. In the present study 58 TgAb-positive schoolgirls were followed up after 5 years of continued iodination. The objectives were: (1) to observe the longitudinal profile of TgAb epitope specificities and (2) to examine the relationship between these specificities and the course of thyroid autoimmunity in this population.
METHODS: Paired subjects' sera (at onset and at 5-year follow-up) were tested for TgAb, thyroid peroxidase antibody (TPOAb), and TgAb epitope-specificity. Epitope reactivity was determined by employing a panel of 10 murine monoclonal antibodies (Tg-mAbs) directed against 6 Tg antigenic clusters (I-VI) in competitive enzyme-linked immunosorbent assay (ELISA) reactions with test sera.
RESULTS: The overall pattern of epitope recognition in individual subject's sera remained preserved over the time period. Nine subjects showed restricted specificities while majority of the subjects were broadly heterogeneous. At follow-up, median TgAb concentration in the restricted group was higher than in the unrestricted (1650 versus 110 kIU/L; p < 0.005). Epitope specificity was a stronger determinant of TgAb persistence than the height of the initial TgAb response or the TPOAb status of subjects.
CONCLUSION: Tg epitope reactivity pattern in
iodised populations may identify subjects at greater risk of
developing autoimmune thyroid disease (AITD)."
Evolution of thyroid autoimmunity during iodine prophylaxis--the Sri Lankan experience.Mazziotti G, Premawardhana LD, Parkes AB, Adams H, Smyth PP, Smith DF, Kaluarachi WN, Wijeyaratne CN, Jayasinghe A, de Silva DG, Lazarus JH. Eur J Endocrinol. 2003 Aug;149(2):103-10.
"OBJECTIVE: To study the evolution of thyroid autoimmunity, in relation to the change in goitre prevalence, during 3 Years of iodine prophylaxis in Sri Lanka. METHODS: Two groups of Sri Lankan schoolgirls between the ages of 10.8 and 17.5 Years were studied in 1998 (401 girls) and 2001 (282 girls). A prospective study was performed in 42 schoolgirls who were thyroid autoantibody (Ab)-positive (+ve) in 1998. Anthropometric measures, urinary iodine excretion (UIE), thyroid Volume, free thyroxine, free tri-iodothyronine, TSH, and thyroglobulin (Tg) and thyroid peroxidase (TPO) Ab were evaluated in all 683 girls. RESULTS: Goitre prevalence was significantly lower in 2001 compared with 1998 related to age (2.9% compared with 20.2%) and body surface area (11.6% compared with 40.8%), although UIE was unchanged. Prevalence of thyroid Ab in 2001 was also lower (23.4% compared with 49.9%); among those with the Ab, 34.8% had TgAb alone and 46.9% had a combination of TgAb+TPOAb, compared with 82.0% TgAb alone in 1998. In 2001, subclinical hypothyroidism was more frequent in Ab+ve (6.3%) than Ab-negative girls (1.0%). A cohort of 42 Ab+ve schoolgirls in 1998 (34 with TgAb alone, eight with TgAb+TPOAb) were evaluated again in 2001. Only 10 of them (23.8%) remained Ab+ve (mostly TPOAb+/-TgAb) in 2001. CONCLUSIONS: This study demonstrates that: (1) in 2001, goitre prevalence and thyroid autoimmunity rates were significantly lower than in 1998; (2) the pattern of thyroid Ab was different in the two surveys; (3) in 2001 alone, the occurrence of hypothyroidism was correlated with the presence of thyroid autoimmunity. These results indicate an evolution of thyroid autoimmune markers during the course of iodine prophylaxis, which has not been described before.
Increased prevalence of thyroglobulin antibodies in Sri Lankan schoolgirls--is iodine the cause?Premawardhana LD, Parkes AB, Smyth PP, Wijeyaratne CN, Jayasinghe A, de Silva DG, Lazarus JH. Eur J Endocrinol. 2000 Aug;143(2):185-8.
"OBJECTIVE: Iodine deficiency was the likely cause of a high prevalence of goitre previously in Sri Lankan schoolchildren. Salt iodination was made compulsory in 1993 but there has been no recent study, using modern techniques, of its benefits or harmful effects. METHODS: Three hundred and sixty-seven schoolgirls between the ages of 11 and 16 years had ultrasound thyroid volume, free thyroxine (T4), free tri-iodothyronine (T3), thyrotrophin (TSH), anti-thyroglobulin (TgAb) and thyroid peroxidase (TPOAb) antibodies, and urine iodine concentrations measured. RESULTS: Median ultrasound thyroid volume ranged from 4.8 ml (11-year-old girls) to 8.6 ml (16-year-old girls) with an age-related increase. Median urine iodine concentrations ranged from 105 to 152 microg/l. Free T4 and free T3 were normal in all, but TSH was elevated in four subjects (5. 53-41.29 mU/l). However, the prevalence of TgAb was markedly raised, ranging between 14.3% (11-year-old girls) and 69.7% (16-year-old girls) (P<0.03). In contrast, the prevalence of TPOAb was 10% or less in all age groups. CONCLUSIONS: Normal median thyroid volumes, iodine concentrations and thyroid function would indicate that iodine deficiency is not a major problem in this group. The high prevalence of TgAb, hitherto unreported, most likely reflects excessive iodination of Tg resulting in increased immunogenicity. There is an urgent need to continuously monitor the adequacy and risks of iodination in this population."
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