Endocrine Abstracts

This case highlights the lessons learnt from a patient who was diagnosed 37 years following presentation with abnormal Thyroid Function Tests (TFTs). Mrs ID had a subtotal thyroidectomy in 1983 for thyrotoxicosis and was started on levothyroxine. She was referred to endocrine services in 2003, and was noted to have a small goitre and abnormal TFTs. Follow up consultations concentrated on thyroxine dose adjustment and querying compliance. She had a background of COPD, CVA (2018), Folate and B12 Deficiency and a sister with hypothyroidism. She had a 47 pack-years smoking history. We reviewed her in 2017 (Aged 64 years). She looked anxious, BMI of 16.9 and history of 11kg weight loss (2003-2017). Clinical examination was normal except ?left temporal visual field defect. Following initial consultation, baseline bloods (including albumin) were normal. TFTs (2003-2019) showed persistently elevated fT4 (30-66 pmol/l), with non-suppressed TSH (20-60 Mu/l). Coeliac screen was negative. Chest X-ray was normal. Formal absorption test ruled out issues with compliance/absorption. Interference assay was negative. Her visual field defect led to a pituitary profile, showing normal cortisol, borderline raised IGF-1 (26.4nmol/l) and raised prolactin (710Mu/l). MRI pituitary revealed a 4mm left sided adenoma. Formal visual field testing returned normal. Simultaneously, α-subunit and SHBG were normal. At this juncture, thyrotropin releasing hormone stimulation test showed a normal prolactin response with persistently raised TSH (>100). Reviewing the entire picture, a requested genetic analysis reported “all previously reported pathogenic variants in the thyroid hormone receptor β (THR β) gene have been detected in hormone binding domain (exon 7, 8, 9 and 10)” confirming the diagnosis of thyroid hormone resistance. The challenge lies ahead of explaining the diagnosis to the patient, 16 years following her initial referral to the hospital services. Methodical approach to atypical TFTs is must in every endocrine clinic.