Endocrine Abstracts

JOINT401

Introduction: Thyroid autoimmune diseases are characterized by a wide spectrum of clinical manifestations ranging from hypothyroidism to hyperthyroidism. This case highlights the diagnostic and therapeutic challenges of managing a patient with suspected overlapping autoimmune thyroid conditions.

Case Presentation: A 45-year-old woman was initially diagnosed with hyperthyroidism in 2008. Laboratory findings included TSH 0.004 μIU/ml (reference range: 0.35–4.94) and positive thyroid peroxidase antibodies (anti-TPO >600 U/ml). Thyroid scintigraphy revealed a warm nodule in a normocaptating gland. Tapazole was prescribed but not initiated. She lost follow-up and returned one year later with hypothyroidism (TSH 5.208 μIU/ml). Levothyroxine therapy was initiated and titrated to 50 mg/day, achieving euthyroid status. During pregnancy, the levothyroxine dose was increased to 88 mg/day. The patient remained stable until 2019, when progressive thyroid function normalization allowed dose reduction, culminating in levothyroxine discontinuation in January 2020. Three months later, without levothyroxine, she developed hyperthyroidism symptoms, including tachycardia and insomnia. Laboratory tests showed TSH <0.02 μIU/ml, elevated free T4 (1.52 ng/dl), anti-TPO 692.59 U/ml, and TSH receptor antibodies (TRAb) 8.99 U/l (reference <0.55). Thyroid ultrasound revealed gland enlargement (volume: 11.8 cm³) with an increased Doppler flow. An antithyroid medication was not initiated, and six months later, thyroid function spontaneously normalized (TSH 1.01 μIU/ml, free T4 0.75 ng/dl). The patient remains asymptomatic under regular follow-up.

Discussion: This case demonstrates the diagnostic complexity of thyroid autoimmune diseases, presenting features of both Hashimoto’s thyroiditis and Graves’ disease. The oscillation between hypothyroidism and hyperthyroidism, presence of positive anti-TPO, anti-TG, and TRAb, and the spontaneous normalization of thyroid function suggest a potential overlap syndrome. Factors contributing to disease variability, including immune modulation and external factors, need further investigation.

Conclusion: The clinical features underscores the importance of continuous follow-up and individualized management in patients with autoimmune thyroid disease. Oscillating thyroid function challenges the diagnosis and requires a multidisciplinary approach to optimize patient outcomes and prevent complications.

Keywords: Thyroid autoimmune disease, Hashimoto’s thyroiditis, Graves’ disease, hypothyroidism, hyperthyroidism, oscillating thyroid function