Carbimazole pseudo-resistance: two case reports
Kattepura Madhusudana, Sanjay Saraf, Robert Smith, Mahesh Katreddy & Khaled Ashawesh
Introduction: Weight gain following treatment of hyperthyroidism is well recognised. This may lead to compliance problems both in patients with/without eating disorders and subsequent failure of therapy. We describe two cases where this was successfully managed with supervised in-patient therapy.
Case 1: A 30-year-old overweight lady was diagnosed with Graves disease following childbirth. Thyroid function test (TFT) at initiation of treatment showed free T4 75.6 pmol/l (10.621.0), free T3 40.2 pmol/l (3.25.9) and TSH<0.03 mIU/l (0.44.0). As the initial response to therapy with prophylthiouracil was minimal, she was switched to carbimazole. Despite being on carbimazole 80 mg/day, she continued to be hyperthyroid both clinically and biochemically with free T4 66.8 pmol/l, free T3 30.4 pmol/l and TSH<0.03 mIU/l. During this period she lost 38 kg of weight and had to undergo abdominoplasty. She was admitted for in-patient supervised carbimazole therapy (80 mg) and made excellent progress with TFT showing free T4 21.5 pmol/l, free T3 7.9 pmol/l and TSH <0.03mIU/l (4 weeks post admission). Presently, she has been referred for thyroidectomy.
Case 2: A 47-year-old lady was diagnosed with hyperthyroidism four years previously and treated with carbimazole 20 mg once/day. At the time of diagnosis, TFT showed free T4 40.8 pmol/l, free T3 12.7 pmol/l and TSH<0.03 mIU/l. Despite being on carbimazole for four years, she continued to be hyperthyroid. Up titration of carbimazole dose to 60 mg/day had made no difference, so she was admitted for supervised carbimazole therapy. There was symptomatic and biochemical improvement with free T4 20.2 pmol/l, free T3 7.3 pmol/l and TSH <0.03 mIU/l. She had total thyroidectomy as definite treatment.
Discussion: Though the causes of failure of treatment with carbimazole can be multifactorial, problems with compliance can be very important. We suggest supervised therapy should be considered before resorting to other measures as compliance related problems are more than likely.