Endocrine Abstracts

A 43-year-old African lady initially presented in September 2007 with hypothyroidism (fT₄ 0.6 ng/dl (0.8–2.0) and TSH 110 mU/l (0.3–4.00)). She gave a history of pain in the neck with transient symptoms of thyrotoxicosis. It was felt that she had gone hypothyroid following an episode of subacute thyroiditis and was started on L-thyroxine. Her compliance was questioned as her TSH fluctuated from being high to being suppressed on 25 μg of L-thyroxine a day. The L-thyroxine was stopped in September 2009 when TSH remained suppressed. In January 2010 fT₄ was 1.9 ng/l, fT₃ 4.60 pg/ml (2.10–4.00), and TSH <0.03 mU/l. Thyroid stimulating immunoglobulin (TSI) was 15.9 U/l (<1.5). A diagnosis of Graves’ disease was made with the presence of both TSH receptor stimulating (TSAb) and blocking (TBAb) antibodies and she was started on thiamazole 10 mg a day. She was lost to hospital follow-up after December 2010 (when fT₄ was 1.7 ng/dl, fT₃ 3.7 pg/ml, and TSH <0.03 mU/l). She was re-referred in January 2013. She was still taking 10 mg of thiamazole a day. TSH was still suppressed and her GP queried compliance and wondered whether she should be considered for radioiodine treatment. A repeat blood test showed TSH <0.03 mU/l, fT₃ 5.0 pg/ml, and TSI 12.4 U/l. The thiamazole dose was increased to 30 mg a day. In May 2013 her TSH was 13.54 mU/l, fT₄ 0.6 ng/dl, and fT₃ 1.8 pg/ml. Thiamazole was reduced to 10 mg a day and stopped in July when TSH was 2.33 mU/l. She was restarted back on 10 mg of thiamazole a day in August 2013 when TSH <0.03 mU/l and fT₃ 5.50 pg/ml. Switching between TBAb and TSAb (or vice versa) occurs in unusual patients after L-thyroxine therapy for hypothyroidism or anti-thyroid drug treatment for Graves’ disease.