MON-442 Hypothalamo-Pituitary Dysfunction Secondary To Orbital Radiotherapy For Thyroid Eye Disease A Rare Case

Abstract Disclosure: S.S. Dhage: None. A. Bose: None. A. Cook: None. Introduction and background Hypothalamo-pituitary (HP) dysfunction can occur as a direct consequence of local tumours, surgery for these tumours and as a delayed effect after cranial or whole-body radiotherapy for various cancers including craniopharyngiomas, intracerebral and nasopharyngeal tumours, and haematological malignancies like lymphomas. HP dysfunction can affect various hormones in the HP axis resulting in various hormone deficiencies. As per the European Group on Graves’ orbitopathy (EUGOGO) guidelines, orbital radiotherapy (ORT) is considered an effective second-line treatment for moderate-to-severe and active TED, especially in patients with significant diplopia. Mild retinopathy as a long term sequalae is the most recognised complication in about 3 to 14 % of patients especially in those with hypertension and diabetes. HP dysfunction has not been previously reported in these patients who received ORT for TED. Case report We present case of a patient who received ORT with a total dose of 20 Gy in 12 fractions completed in September 2010 for the treatment of steroid resistant and diplopia predominant TED. Two years following completion of ORT, the patient began experiencing irregular periods, hot flushes, and mood swings but her gonadotrophins and oestradiol remained low normal. Eventually she had cessation of menses but with normal gonadotrophins. She remained on long term low dose steroids due to severe asthma and developed primary hypothyroidism after remission of her Graves` thyrotoxicosis. Symptoms of persistent fatigue, tiredness and lethargy with the background of ORT for TED and early menopause with normal gonadotropins, prompted further evaluation of possible growth hormone (GH)deficiency due to HP dysfunction. Her adult GH deficiency assessment (AGHDA) score was 23/25 and peak GH level was 1.13 ug/L on insulin tolerance test (ITT); which confirmed diagnosis of adult GH deficiency. Discussion and Conclusion Despite radiotherapy induced HP dysfunction being extensively reviewed in literature, these cases have not been associated with ORT for TED. ORT is often described as an effective and safe treatment option for TED with no major adverse events even after long term follow up. This case highlights a potential association between orbital radiotherapy for Graves' TED and development of hypopituitarism as a long-term complication. There are no studies or research linking hypopituitarism to ORT. This case proposes a potential need of long-term endocrine monitoring in patients undergoing ORT to detect and manage potential complications such as hypopituitarism. Presentation: Monday, July 14, 2025