SUN-332 - Prolonged Thyroiditis Following Umbilical Cord-Derived Stem Cell Therapy: A Case Report of Severe, Steroid-Dependent Hyperthyroidism

Background: Stem cell-based therapies are increasingly utilized internationally for musculoskeletal conditions, often outside regulated clinical frameworks. While immune-mediated adverse effects have been reported, endocrine complications remain poorly characterized. Thyroiditis following stem cell therapy has rarely been described. We present a case of severe thyroiditis following umbilical cord derived stem cell injections.

Case Presentation: A 67-year-old male with no prior thyroid disease presented with new-onset hyperthyroidism characterized by tachycardia, weight loss, insomnia, tremors, visual disturbance, and muscle wasting. Symptoms developed approximately one month after receiving umbilical cord-derived stem cell injections to multiple joints, including the ankle, knee, hips, shoulder, wrist, and sacroiliac joints, performed in Costa Rica. He had previously undergone autologous stem cell therapy six years earlier without complication.
Initial evaluation revealed suppressed TSH at 0.01 with progressively rising free T4 levels from 6.6 to greater than 8.0. Thyroid autoantibodies, including TSI, TRAb, and TPO antibodies, were negative. He had discontinued chronic iodine supplementation one month prior to symptom onset and was not taking biotin. There was no history of intravenous contrast exposure.
Radioactive iodine uptake and scan demonstrated markedly low uptake consistent with thyroiditis. Due to worsening thyrotoxicosis, he required high-dose glucocorticoids with Prednisone up to 40 mg daily, a beta-blocker, temporary Lithium therapy, and Cholestyramine. Lithium and Cholestyramine were discontinued after improvement in free T4 levels.
His clinical course was notable for prolonged steroid-dependent thyroiditis with recurrence following early glucocorticoid withdrawal. Over six months, thyroid hormone levels gradually normalized with a slow Prednisone taper. At six months following stem cell therapy, he achieved biochemical euthyroidism on low dose Prednisone at 5 mg daily with resolution of systemic symptoms. He was weaned off prednisone completely by eight months and remains euthyroid off steroid therapy at nine months post-stem cell therapy.

Conclusion: This case highlights a severe and prolonged thyroiditis temporally associated with umbilical cord derived stem cell therapy. The absence of thyroid autoimmunity, low radioactive iodine uptake, and steroid responsiveness support an inflammatory mechanism. Clinicians should be aware of potential endocrine complications related to unregulated stem cell therapies. Further surveillance is needed to better define the endocrine safety profile of these interventions.

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