Endocrine Abstracts

A 56 years old lady was referred to our endocrine service for further management of levothyroxine replacement. She was diagnosed with Graves’ disease 26 years ago and underwent thyroidectomy as definite treatment. Post-operatively, she was commenced on 100mcg of levothyroxine and continued to have regular follow up with her GP. It was noted that her levothyroxine dose had to be reduced to 50 mcg daily over a period of 10 years due to persistently suppressed TSH levels with free T4 levels within the normal range. In January 2015, her thyroid function showed a picture suggestive of over-replacement with TSH <0.01 (0.3–4.2) milliunit/l, free T3 of 6.3 (2.5–5.7) pmol/l and free T4 of 24 (9–23) pmol/l. Therefore, her thyroxin dose was further decreased to 50 mcg on alternate days by her GP. In November 2016, she was seen in our endocrine clinic while on the above levothyroxine regimen. She didn’t report any symptoms related to thyrotoxicosis or over-replacement. Repeat thyroid function sowed TSH of 0.01 (0.3–4.2) milliunit/l, free T3 of 4.3 (2.5–5.7) pmol/l, free T4 of 14.5 (9–23) pmol/l and a positive TSH receptor antibody level of 2.9 (<0.4) unit/ml. Levothyroxine was withheld and she underwent a thyroid ultrasound that showed three hypervascular nodules (thyroid remnants) in the thyroid bed. A technetium uptake scan was suggestive of multiple toxic nodules: two large nodules in the left with high increased tracer uptake and another smaller nodule in the right mid pole of the thyroid with low level activity. Four months after discontinuing thyroxin, the patient was clinically euthyroid with TSH of 2.25 (0.3–4.2) milliunit/l, free of T3 3.7 (2.5–5.7) pmol/l and free T4 of 10 (9–23) pmol/l. She remains under regular surveillance as she is at high risk of Graves’ disease recurrence.