Phenotypic Expression and natural history of an atypical case of Graves Disease : Cyclical Graves' disease - A case report

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 449-497-Thyroid Neoplasia & Case Reports
Clinical
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-480
Wei Chong Dayrl Tan*, Cherng Jye Seow and Rinkoo Dalan
Tan Tock Seng Hospital, Singapore, Singapore
Introduction

Usually Graves’ disease is characterised by a period of hyperthyroidism and if treated with anti thyroid drugs for a period of 18-24 months, can be followed by a remission or develop a recurrence of hyperthyroidism. Rarely, they may have alternating periods of hyperthyroidism and hypothyroidism with unexpected spontaneous fluctuations of thyroid hormone status during the course of follow up. We present a patient who initially had subclinical hyperthyroidism, followed by a period of hypothyroidism, which rebounded back to overt hyperthyroidism during the course of follow up.

Case Presentation

A 67-year old lady was initially seen for asymptomatic subclinical hyperthyroidism - fT4 15 pM (RI:8-21), TSH < 0.01 mIU/L (RI: 0.34-5.60). TRAb levels were elevated at 10.9 IU/L (RI: <0.4). There was no goitre clinically detected. However, at the next outpatient visit, even before thioamides were initiated, she was hypothyroid - fT4 5 pM, TSH 81.56 mIU/L. Thyroid receptor blocking antibody was 10% (<71% indicate blocking) and a diagnosis of Graves’ disease with blocking antibodies was made. She was started on thyroxine replacement. However upon review 3 months later, she was thyrotoxic again with - fT4 53 pM/L, TSH 0.02 mIU/L. She was thus started on thionamides and referred for   radioactive iodine (I-131) therapy. After I-131 therapy, she developed hypothyroidism requiring lifelong thyroxine replacement.

Discussion

Cyclical Graves' disease is an uncommon distinct presentation of Graves' disease, mediated by oscillations in the ratio of concentrations of stimulatory to blocking TSH receptor antibodies at different time intervals. Thyroid stimulating antibodies cause thyrotoxicosis and TSH receptor blocking antibodies cause hypothyroidism. TSH receptor antibody levels are elevated in affected patients and blocking activity is detected upon measurement of TSH receptor blocking antibodies at the time of hypothyroidism (1). In our patient and patients reported in the literature most of the patients had a very small goitre in contrast to the usual enlarged diffuse goitre seen in typical Graves’ disease (1).

Conclusion

Unexpected spontaneous fluctuations of thyroid hormone status can occur during follow-up of Graves’ disease patients.  These patients usually have very small goitres and definitive treatment in the form of  I-131 or thyroidectomy during the hyperthyroid phase is recommended.

(1)  Cho BY, Kim WB, Chung JH,Yi KH,Shong YK, Lee HK, Koh CS. High prevalence and little change in TSH receptor blocking antibody titres with thyroxine and anti thyroid drug therapy in patients with non goitrous autoimmune thyroiditis. Clin Endocrinol 1995;43:465-71.

Nothing to Disclose: WCDT, CJS, RD

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