SAT-324 - Postpartum Thyroid Storm and Stroke in Graves' Disease Complicated by Moyamoya Vasculopathy and Massive Thyromegaly

Moyamoya disease is a rare, progressive cerebrovascular arteriopathy that predisposes to ischemic stroke, particularly in young women. Graves’ disease causing Moyamoya is uncommon but clinically important, as untreated hyperthyroidism can lead to thyrotoxicosis, worsening cerebral hemodynamic instability and increased stroke risk in these patients. This case highlights the diagnostic and management considerations of this rare association.
A 24-year-old African American woman with known Graves’ disease, hypertension and poor adherence to methimazole, presented three months postpartum in March 2025 with palpitations, severe tachycardia, tongue numbness, and right arm weakness. She was diagnosed with thyroid storm (TSH < 0.01 µIU/mL, [n = 0.35uIU/mL to 4.94 uIU/mL], free T4 >5.0 ng/dL, [n = 0.70 ng/dL to 1.48 ng/dL]) complicated by an acute ischemic stroke, and additional imaging revealed underlying Moyamoya disease. She was initially treated with propylthiouracil, glucocorticoids, beta-blockade, and Lugol’s iodine, but PTU was discontinued due to transaminitis and replaced with high-dose methimazole. Evaluation supported classic Graves’ disease, including markedly positive TSI antibodies 4.34 IU/L [normal ≤ 0.55 IU/L] and thyroid ultrasound demonstrating a massively enlarged gland with heterogeneous echotexture. Free T4 normalized over several months, followed by hypothyroidism by late 2025, as a result, her methimazole dose was reduced.
Moyamoya disease is a progressive condition with high cerebrovascular risk. Hence, the patient underwent right craniotomy with encephaloduroarteriosynangiosis in January 2026, complicated by postoperative subdural hematoma requiring evacuation and decompressive craniectomy. She is now scheduled for thyroidectomy for definitive management of her hyperthyroidism.
This case illustrates the rare but clinically significant association between Graves’ disease and Moyamoya. Moyamoya disease is more prevalent among young East Asian women. In African American patients, Moyamoya disease is more commonly associated with Sickle cell disease or systemic lupus erythematosus; however, no alternative vasculopathy was identified in this patient, implicating Graves’ disease as the likely contributor.

Proposed mechanisms include autoimmune-mediated vascular injury and thyroid hormone-induced endothelial dysfunction. In this patient, thyroid storm precipitated cerebral hemodynamic stress that unmasked previously compensated Moyamoya vasculopathy and culminated in ischemic stroke. This case highlights the importance of early treatment of hyperthyroidism and multidisciplinary planning for definitive thyroid therapy in high-risk patients to reduce the risk of recurrent cerebrovascular events.

*Unless otherwise noted, all abstracts presented at ENDO must not be released to the press or the public until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.*