Endocrine Abstracts

Introduction: Deranged thyroid function tests are frequently referred to the endocrine team and are generally secondary to the assay interference.

Case report: We Report a case of 33 years old lady referred with symptoms of dizziness, palpitations, cold intolerance and poor sleep with no associated tremors or weight changes. No goiter was observed on clinical examination. Thyroid function test showed abnormal hormone levels of T4 (32 pmol/l) and TSH (3.11mu/l) with negative TPO (12.2 IU/ml) and thyroid stimulating antibodies (0.13 IU/l). Thyroid function test was then rechecked to assess for methodological interface and results were consistent with raised TSH (23.50 mul/l) with raised free T4 (20.8 pmol/l) and T3 (5.7 pmol/l). Further history suggested patient’s development was delayed during early years with no suggestion of thyroid disorders in family. MRI pituitary was normal with no evidence of pituitary adenoma. In view of symptoms she was initiated on carbimazole 10mg once daily with slight improvement. Genetic testing for familial dysalbuminaemic hyperthyroxinameia was also negative. Weaning off of carbimazole resulted in worsening patient’s symptoms. 2013 European thyroid association guidelines for Thyrotropin secreting pituitary tumors were reviewed in Endocrine MDT and in view of patient being symptomatic it was deemed reasonable to proceed with TRB gene testing than dynamic testing with TRH or T3 suppression test. Genetic testing for TRB gene are waited.

Conclusion: Deranged thyroid function test can present as a conundrum in clinical practice. Thyroid Hormone resistance is a rare autosomal dominant genetic syndrome with TRB gene mutation in 80-85% patients. Pituitary thyroid hormone resistance is typically associated with goitre and symptoms related to thyrotoxicosis. Family history remains crucial in guiding the diagnosis. TSHoma remains the main differential with evidence of pituitary adenoma in 30% of patient.