Endocrine Abstracts

JOINT3406

Background: Graves’ disease (GD) is an autoimmune disorder that leads to hyperthyroidism, primarily due to the activation of the thyroid gland by thyrotropin receptor antibodies (TRAb). GD in children is rare, and its occurrence in monozygotic twins is even more uncommon. This case explores the potential genetic and environmental factors contributing to GD in twins.

Case Presentation: A 3-year-old female (a preterm product of an IVF, part of a monozygotic twin). was otherwise healthy except for mild eczema. She presented with six months history of intermittent loose stools, mild abdominal discomfort, and later, increased appetite, hyperactivity, insomnia, and palpitations. Clinical evaluation revealed tachycardia (HR 150-160 bpm), elevated Free T4 (>65 pmol/L), and suppressed TSH (<0.01 mIU/L), confirming hyperthyroidism. Thyroid antibody testing was positive for Anti-TG Ab (232 IU/L), Anti-TSHR Ab (27.5 IU/L), and elevated TPO antibodies (213 kIU/L). Goiter grade I in examination. Neck ultrasound showed a mildly enlarged thyroid with hyperemia. The patient was treated with carbimazole and propranolol, leading to gradual improvement. The second twin, despite positive thyroid antibodies (TSHR Ab <0.8, TPO 51, Anti-TG Abx 647 IU/ml), remain euthyroid.

Literature Review: Graves’ disease (GD) in monozygotic twins is rare, with few cases reported, especially in this age group. Genetic factors, including shared HLA alleles and thyroid-specific antibodies, may predispose twins to autoimmune thyroid disorders. A 2019 study by Smith et al. described a case where one twin developed GD while the other remained euthyroid, despite both having thyroid antibodies, highlighting the complex interaction between genetic predisposition and environmental factors like infections, stress, or maternal thyroid dysfunction. Del Giudice et al. (2018) found that monozygotic twins are at a higher risk for GD than dizygotic twins, emphasizing the role of genetics. However, environmental triggers may determine whether one twin develops the disease while the other stays asymptomatic.

Discussion: The presence of thyroid antibodies in the second twin, despite euthyroid status, suggests an increased future risk for GD. The published Literature supports the observation that elevated TRAb levels can precede clinical disease and may serve as a biomarker for early intervention. This case underscores the importance of monitoring for GD in siblings with positive thyroid antibodies, especially in the context of family history..

Conclusion: This case of monozygotic twins with divergent thyroid outcomes underscores the complex interplay of genetic and environmental factors in autoimmune thyroid disease. Early detection and monitoring of at-risk individuals are crucial.