Endocrine Abstracts

Section 1: A 77 year female was referred by her GP in May 2019 for abnormal thyroid function tests (TFT) which were requested due to new diagnosis of atrial fibrillation. The patient was otherwise asymptomatic and clinically euthyroid. Family History was negative for thyroid abnormalities. On enquiry, the patient revealed that she had abnormal thyroid function tests associated with a large goitre in 1970s and subsequently underwent partial thyroidectomy followed by radioactive iodine treatment.

Section 2: Thyroid profile trend is shown in Table 1. Anti-TSH receptor Antibodies and TPO Antibodies were negative. Full pituitary profile and MRI brain were done to rule out pituitary disease and were normal. Cortisol and sex hormone binding globulin were normal. Thyroid ultrasound and thyroid uptake scan were consistent with nodular thyroid disease. The nodules were considered benign and she was referred to ENT team for further follow up.

Section 3: Genetic testing confirmed pathogenic variant of Thyroid hormone receptor beta (THRB) gene. A single base change c.1312C>T, in exon 10 of THRB was detected that led to abnormal THRB protein p.Arg438Cys, resulting in thyroid hormone resistance. Considering the patient was clinically euthyroid and asymptomatic, conservative management with regular follow up of TFT was implemented.

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Section 4: Thyroid hormone resistance (THR) is a rare disorder and should be suspected with atypical TFT. As may have happened in this case, failure to recognise an uninhibited TSH in the presence of elevated thyroid hormones and goitre may lead to unnecessary treatment with thyroidectomy and radio-iodine treatment. When treating these patients it is important to understand that elevation of T3 and T4 are compensatory to the degree of thyroid hormone resistance. Clinical presentation is variable, patients may be clinically euthyroid, hyperthyroid, hypothyroid or mix of hypothyroid symptoms in some organs and hyperthyroid in others. Treatment is largely symptomatic depending on the symptoms (e.g. with beta blockers for tachycardia). Goitre is one of the most common symptoms and tends to reoccur after surgery and radio-iodine treatment. If there are compressive symptoms due to goitre then treatment with thyroid hormone supplementation can be considered with aim to bring TSH level in the upper limit of the normal.