Conversion to Graves disease from Hashimoto thyroiditis: a study of 24 patients

ABSTRACT Objective: The conversion of Hashimoto's thyroiditis (HT) to hyperthyroidism due to thyrotropin receptor antibodies is intriguing and considered rare. The contribution of TSH receptor blocking antibodies (TRAb), which may be stimulators (TSAb) or blockers (TBAb), is suspected. We describe clinical and biological variables in a series of patients switching from Hashimoto's thyroiditis to Grave's disease. Subjects and methods: Retrospective case study of 24 patients with Hashimoto's thyroiditis followed during 48 ± 36 months that developed later Graves' disease (GD). These variables were analysed in the hypo and hyperthyroid phase: age, sex, initial TSH, free triiodothyronine (fT3), free thyroxine (fT4), anti-TPO, TBII antibodies, parietal cell autoantibodies, time between hypo and hyperthyroidism, thyroid volume and levothyroxine doses (LT). Results: In HT, mean TSH was 9.4 ± 26.1 UI/L and levothyroxine treatment was 66.2 ± 30.8 µg/day. The switch to GD was observed 38 ± 45 months after HT diagnosis. As expected, we found significant differences on TSH, FT3, FT4 and TBAb levels. Three out of 14 patients had parietal cell autoantibodies. In two of these three cases there was an Helicobacter pylori infection. There were no significant differences between HT and GD groups with respect to thyroid volume. Conclusions: To our knowledge, large series documenting the conversion of HT to GD are scarce. Although rare, this phenomenon should not be misdiagnosed. Suspicion should be raised whenever thyroxine posology must be tapered down during the follow-up of HT patients. Further immunological and genetic studies are needed to explain this unusual autoimmune change.

Urinary iodine status and thyroid dysfunction: a Bangladesh perspective.

Iodine deficiency is endemic in Bangladesh. Compulsory iodization of table salt was introduced since 1993 to prevent and improve thyroid disorders in the country. Urinary iodine status, thyroid function and antithyroid antibodies were studied in 397 newly diagnosed thyroid patients and 94 age-sex matched controls. Among thyroid patients, 96 were hyperthyroid, 185 euthyroid and 116 hypothyroid. Mean and median urinary iodine were higher (p=0.075) in thyroid patients (26.13+/-0.91 and 23.03) than controls (22.65+/-1.47 and 18.59); in hyperthyroid and euthyroid than hypothyroid (p=0.020); in multinodular (28.08+/-2.80 and 26.94) and diffuse (27.35+/-1.19 and 26.71) goitre than uninodular (23.91+/-2.37 and 19.14) and nongoitrous (NG, 21.5+/-2.05 and 18.27) (p=0.098) patients but no sex difference (p=0.466). Antimicrosomal (26.7%) and antithyroglobulin (34%) antibodies were more frequently positive among thyroid patients than controls (6.4% and 12.8% respectively) (p=0.00002 and p=0.00005 respectively). Antibody positivity was higher in diffuse (82/228) and multinodular (20/47) goitre than nongoitrous (20/56) and uninodular (13/66) goitre (p=0.046) as well as in hypothyroid (55.2%) and hyperthyroid (36.5%) than euthyroid (19.5%) patients (P<0.001). Urinary iodine correlated neither with antimicrosomal (thyroid patients: p=0.597 and control: p=0.112) nor with antithyroglobulin (thyroid patients: p=0.388 and control: p=0.195) antibody. Thyroid autoimmunity and dysfunction seems common; and interaction of salt iodization with iodine status and thyroid disorders may be important in Bangladesh.

Clinical, biochemical and cytomorphological observations in juvenile chronic lymphocytic thyroiditis.

OBJECTIVE: To determine the clinical, biochemical, ultrasonological and cytomorphological features in goitrous juvenile chronic lymphocytic thyroiditis(CLT). SETTING: Tertiary referral center for thyroid disorders. SUBJECTS: A total of 455 children were evaluated for goiter. Of these 122 children had features of CLT in FNAC and were further studied. METHODS: All subjects were subjected to detailed clinical examination. The thyroid functional status was assessed by estimation of serum concentration of thyroid hormones (thyroxine and triiodothyronine) and thyrotropin (TSH). In addition the antithyroid antibody titers were measured. Ultrasonological and cytomorphological characteristics in these patients were also evaluated. RESULTS: The mean age at presentation was 12.5 years (SD 3.93). The male: female ratio was 1:7.7. Thyroid functional status as assessed by serum thyroxine and thyrotropin levels revealed, euthyroidism in 67 (54.9%), hypothyroidism in 30 (24.6%), subclinical hypothyroidism in 22 (18%) and hyperthyroidism in 3 (2.5%). Thyroid antimicrosomal antibodies were detected in significant titers in 90 (73.8%) and antithyroglobulin was positive in 71 (58.2%). The positivity of the antimicrosomal and antithyroglobulin antibodies were much higher in subjects with hypothyroidism and was detected in 86.5% and 69.2%, respectively. The mean urinary iodine excretion was 74.1 micrograms/g of creatinine (SD 31.4) indicating mild iodine deficiency. Fine needle aspiration cytoloty (FNAC) revealed features of chronic lymphocytic thyroiditis. Hurthle cell changes was seen in only 12% of the cases. The epithelium was more often hyperplastic and vacuolation of the cytoplasm and peripheral vacuolations were seen frequently. Giant cells and epithelioid cells were seen in many cases. CONCLUSIONS: In any child presenting with firm goiter, a diagnosis of CLT should be excluded. Many subjects with juvenile CLT have biochemical evidence of hypothyroidism but only few symptoms or clinical features.