A 36-year-old woman received isotretinoin treatment for acne and shortly after developed a silent thyroiditis. A 26-year-old woman likewise was treated with isotretinoin for acne and developed Graves' disease two and a half months after treatment. Both patients were without personal or familiar history of thyroid disease. These case reports describe two young women who in proximity to treatment with isotretinoin developed thyroid disease. We propose screening for development of thyroid disease as a part of the already established control regime for isotretinoin patients.