Endocrine Abstracts

68 years old female initially referred to endocrine clinic in November 2016 for assessment of fluctuating thyroid function. She had a history of long standing primary hypothyroidism, stable on treatment with 100 mcg Levothyroxine. In last one year, Levothyroxine was tapered and stopped due to persistent suppression of TSH and high normal Free T4. Last tests showed TSH of <0.01mIU/l and Free T4 of 27.1 pmol/l. She had ongoing complaints of feeling increasingly tired and generally unwell. She was clinically euthyroid with no evidence of thyroid eye disease. There was asymmetrical thyromegaly on right side with no compressive symptoms. Her thyroid function tests (TFTs) were normal with negative thyroid antibodies. Her TSH was 0.31 (0.27–4.20 mIU/l), T4 11.1 (10–23 pmol/l) and T3 5.9 (3.1–6.8 pmol/l). However, thyroid ultrasound showed a 2.7×3.5 cm right lobe nodule, characterised as U2. Repeat blood test revealed suppressed TSH (0.06 mIU/l), normal T3 (5.8 pmol/I) and T4 (12 pmol/l). Pituitary profile was normal for age. Suppressed TSH with increased T3/T4 ratio raised suspicion of a toxic nodule. She had a thyroid technetium uptake scan which confirmed dominant nodule in the right lobe of the thyroid. She was planned for Radio Active Iodine treatment but her thyroid function normalised and a decision was made to keep her under active surveillance. Over last 6 months, she had normal TFTs twice with improvement in symptoms. This is good learning case showing fluctuating toxic features in a thyroid nodule.