Thyroid Hormone Resistance in Identical Twin Sisters with Atrial Fibrillation: Case Report and Review of the Literature.

Journal of Endocrinology and Diabetes
Mark B Zimering

Abstract

To report identical twin sisters harboring the A317T mutation in the thyroid hormone beta receptor gene (TR β) who developed atrial fibrillation and refractory congestive heart failure in the sixth decade of life. To critically assess whether the A317T mutation may be responsible for increased cardiotoxicity compared to other thyroid hormone beta receptor gene mutations. A 59-year-old woman referred for evaluation of abnormal thyroid function tests had been experiencing frequent spells of tachycardia associated with dyspnea, and dizziness necessitating multiple hospitalizations. Elevation in free thyroxine (T4), total triiodothyronine (T3) and inappropriately normal thyroid stimulating hormone (TSH) was consistent with a clinical diagnosis of thyroid hormone resistance. Magnetic resonance imaging of the brain was negative for a TSH-secreting pituitary adenoma. A blood sample was sent for thyroid hormone receptor gene mutational analysis, but it would require eight weeks to complete processing. A modified L-T3 suppression test was used to assess thyroid-pituitary axis feedback. After three weeks' of cytomel (L-T3) (25 micrograms daily) TSH decreased by 50%, and free T4 level decreased by 22% compared to baseline levels. Genetic ...Continue Reading

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