Unexpected cure of a toxic nodule in a multinodular goiter induced by immune checkpoint inhibitors: a case report

INTRODUCTION: Immune checkpoint inhibitors (ICI) are used to treat cancers including metastatic melanomas and can induce endocrine side effects. The thyroid is frequently affected with classically transient thyrotoxicosis followed by hypothyroidism. The evolution of thyroid nodules and goiters under ICI therapy is poorly described. CASE PRESENTATION: A 72-year-old male presenting with hyperthyroidism due to a toxic nodule in a multinodular goiter (MNG) started ICI therapy combining ipilimumab and nivolumab to treat metastatic melanoma. After an initial worsening of thyrotoxicosis, treated with carbimazole, he developed profound hypothyroidism, persisting after carbimazole discontinuation, needing a long-term levothyroxine supplementation. Ultrasound control performed 6 months after ICIs treatment initiation revealed diffuse thyroid atrophy with involution of all nodules. (123)I-scintigraphy confirmed a destructive mechanism. DISCUSSION: The evolution of MNG and toxic nodules is poorly described in patients treated with ICI since systematic US evaluations are lacking. We describe for the first time a toxic nodule cured by ICI therapy inducing destructive thyroiditis. CONCLUSION: Pre-existing nodules and MNG, even if toxic, are not a contraindication for ICI treatment provided the patients are carefully monitored.