Introduction: Resistance to thyroid hormone (RTH), a syndrome reduced end-organ responsiveness to thyroid hormone.
Case report: A 42 year old woman underwent near total thyroidectomy due to her enlarged thyroid with multiple nodules. At that time she had sligthly elevated values of plasma FT4, FT3 and normal TSH values and had no sign and symptoms of thyrotoxicosis or hypothyroidism. After thyroidectomy she recieved L-T4 treatment but her TSH levels remains elevated although FT4 was high. She was reffered endocrinology polyclinic when she began to have symptoms of hypothyroidism like fatique, fibromyalgia. The results were FT4: 1.93 ng/dl (n: 0.611.12), FT3: 2.2 pg/ml (n: 2.53.9) TSH>100 uIU/ml (n: 0.274.2) under 150 mcg L-T4 treatment. There were no detectable anti-thyroid autoantibodies. Alpha subunit of TSH level was 0.8 IU/l (n: 00.8) normal. No pituitary adenoma was determined in pituitary MRI. She has no family history of thyroid disease. Genetic test is not available in our hospital. We performed TRH stimulation test after taken off levothyroxine for 14 days and TSH diluted up to 20 times during test. After intravenous bolus injection of TRH (200 mcg) serum TSH concentration increased from 269 uIU/ml (basal value) to a peak of 1330 uIU/ml at 30 min. As a result RTH was considered and LT4 initiated again. After L-T4 titrated up to 175 mcg a day L-T3 added 12.5 mcg two times a day. Six weeks after this treatment FT4: 2.58 ng/dl (n: 0.611.12), FT3: 3.99 pg/dL (n: 2.53.9), TSH: 14 uIU/ml sn: 0.274.2). Her complaints were reduced. Blood pressure was 120/80 mmHg, pulse 74/min. She was clinicaly better.
Conclusion: Treatment with L-T3 would be more appropriate for reducing goitre size than attempting thyroidectomy in that patient. In patients with RTH thyroid gland ablation tends to aggravate thyroid dysfunction and multinodularity. Large glands have been successfully treated by administration of a single high dose of L-T3 given every other day. Symptoms of thyrotoxicosis usually respond to the administration of the beta bloker, atenolol.
20 - 23 May 2017
European Society of Endocrinology