Endocrine Abstracts

A 32-year-old female was referred with abnormal thyroid function tests after investigation for nonspecific joint symptoms and exhaustion in 2010. Initial biochemistry showed TSH 0.03 mU/l(0.2-5), Free T4 75 pmol/l(9-24). At her endocrine appointment she reported loose stools, tremors, exertional dyspnea and a peculiar sensation in neck in keeping with thyrotoxicosis. Since puberty, she had problems acquiring weight. Repeat thyroid function demonstrated TSH <0.01 mU/land Free T4 97.6 pmol/l. Carbimazole was initiated alongside propranolol and she felt marginally better after taking the prescription for a few days, so she stopped taking it and ceased follow up. Due to several unsuccessful appointments, she was discharged from the service. She returned to the service eight years later with the same symptoms. She was now experiencing ophthalmic issues. TSH was 1.2 mu/land Free T4 was 35.4 pmol/l. Thyroid peroxidase antibodies and TSH Receptor antibodies were positive in keeping with autoimmune thyroid disease. Thyroid US was normal. There was a family history of thyroid disorders, with her mother and maternal grandmother having thyroidectomy. Two of her children had type 1 diabetes and one was reported to have a thyroid problem. Carbimazole and propranolol were prescribed for Graves’ disease. Despite significant carbimazole doses her symptoms persisted. She switched to propylthiouracil after believing she had issues with carbimazole but later reported varied compliance. She represented in 2022 with palpitations, hot flushes, tremor, insomnia, amenorrhea and altered bowel habit, predominantly diarrhoea. She had continued propranolol but was intermittently taking propylthiouracil. She reported dry, gritty eyes but clinical activity score was 0/7. Smoking cessation and eye lubricants were advised. Investigations revealed TSH 0.64 mU/l, Free T4 37.0 pmol/l. This pattern had persisted over several years and TSH hadn’t been suppressed since initial presentation. History was in keeping with Graves’ disease but underlying thyroid hormone resistance was also suspected. Propylthiouracil was ceased and symptoms were managed with titration of propranolol. Subsequent testing confirmed a pathogenic missense mutation in TRHB gene.

Conclusion: Graves’ disease is common and strong family history alongside positive antibody titres and clinical features are supportive of the diagnosis. Variable compliance with medications can make interpretation of results difficult but careful assessment of trends and spotting anomalies is vital to ensure alternate diagnoses aren’t missed, particularly when dual pathologies can co-exist. Thyroid hormone resistance is rare and treatment revolves around symptomatic management.