Endocrine Abstracts

Thyroid eye disease (TED) management and treatment options have expanded recently to include multiple new monoclonal antibody treatments which are proving very effective. Teprotumumab is one such drug and is an anti IGF-1R monoclonal antibody. We report on the case of a 60-year-old female, diagnosed with Graves’ Disease (GD) in 2014, for which she underwent a thyroidectomy in 2015 for definitive treatment. She suffered from severe TED. A pituitary macroadenoma was picked up in 2016 incidentally on an MRI of her orbits. The adenoma was non-functioning and serial scans had shown slow growth over 10 years. She was initiated on Teprotumumab in September 2022 for worsening TED. Prior to initiation, her bloods revealed a normal pituitary profile, including a normal IGF-1 of 19nmol/l. Due to growth of her adenoma, headaches, poor vision and unreliable visual field testing due to her TED, she was referred to Neurosurgery for trans-sphenoidal surgery. She was found to have an IGF-1 level of 83nmol/l in February 2023, further increasing to 104nmol/l in October. The elevated IGF-1 levels were assumed to be secondary to Teprotumumab, however the decision was made to further investigate to exclude underlying acromegaly. A growth hormone suppression test, an insulin tolerance test, pituitary profile and serial visual field tests performed were normal. After MDT discussion she had trans-sphenoidal surgery to remove her pituitary tumour in April 2024. Histology revealed a silent corticotroph adenoma. This case highlights the importance of understanding the mechanism of action of newer medication used to treat TED. Teprotumumab is a monoclonal antibody against IGF-1R. This results in high serum IGF-1 levels and can cause confusion in patients who have co-existing pituitary adenomas.