Endocrine Abstracts

Graves’ disease is an autoimmune disease with thyroid stimulating immunoglobulins (TSI) causing hyperthyroidism. Anti-thyroid drugs are used for disease control pending spontaneous remission and radioiodine or thyroidectomy are definitive treatment resulting in the need for lifelong levothyroxine treatment. We present two cases where total thyroidectomy was not curative due to the presence of ectopic thyroid tissue not identified at time of surgery. Case 1, aged 32, female. Thyrotoxic with fT4 45.2 pmol/l, fT3 19.6 pmol/l, TSH <0.02 mU/L and TSI 11.6 IU/l. Mild/moderate thyroid eye disease present. Following treatment with carbimazole 40 mg od for two weeks – fT4 23.1 pmol/l, fT3 7.4 pmol/l and TSH <0.02 mU/L but a rise in transaminase suggested hepatotoxicity. Radioiodine ablation declined, therefore total thyroidectomy undertaken. Case 2, aged 52, female. Thyrotoxic with fT4 >76.2 pmol/l, fT3 >46.1 pmol/l, TSH <0.02 mU/L and TSH receptor antibodies 28.5 U/l. Mild/moderate thyroid eye disease present. Treatment with a block replacement regime of carbimazole 40 mg plus levothyroxine 100 mg od resulted in euthyroidism but with relapses four and nine years after stopping treatment. Total thyroidectomy undertaken. In both cases there was a decrease in requirement for post-operative levothyroxine replacement progressing to total withdrawal. Hyperthyroidism then returned. Tc-99m pertechnetate scan demonstrated a solitary foci in case 1 and 2 foci of uptake in case 2. Case 1 opted for further medical treatment and case 2 further surgical intervention which was successful. Following subtotal thyroidectomy if Graves’ disease remains active there is a risk of recurrence of hyperthyroidism. Post-total thyroidectomy recurrence of hyperthyroidism is rare even in active Graves’ disease but can occur in the presence of ectopic thyroid tissue. Pre-operative isotope scanning is not justified on cost grounds due to the rarity of this phenomenon.