Unilateral Graves' Orbitopathy Followed by Hashimoto's Hypothyroidism: Highlighting Micronutrient Influence in Thyroid Autoimmunity.

We present the case of a 19-year-old female who initially exhibited unilateral orbital symptoms and laboratory evidence of autoimmune thyroid involvement, consistent with a diagnosis of euthyroid Graves' orbitopathy (GO). She responded well to immunosuppressive therapy and remained clinically stable for two years. Subsequently, she developed fatigue, menstrual irregularities, and mild recurrent eye discomfort. Laboratory evaluation revealed biochemically severe hypothyroidism with elevated thyroid-stimulating hormone (TSH), low free thyroxine (FT4), and persistently high thyroid peroxidase antibodies (anti-TPO). Additional findings included iron deficiency anemia and vitamin D deficiency. Thyroid ultrasound confirmed features of autoimmune thyroiditis, and she was started on hormonal and micronutrient replacement therapy. This case highlights a rare clinical evolution from euthyroid GO to Hashimoto's thyroiditis (HT) and emphasizes the need for long-term follow-up in autoimmune thyroid conditions. It also suggests that micronutrient status may influence immune shifts and disease progression, underscoring the importance of addressing modifiable factors as part of comprehensive endocrine care.