Alternating Thyroid Status Between Thyrotoxicosis and Hypothyroidism in a Patient with Varying Antithyroid Antibodies

Abstract

Objective: Autoimmune pathologies are a growing aspect of medicine. Knowledge about atypical cases is essential. This report will describe a case of unusual, alternating fluctuations in thyroid function. Abbreviations: FT4 = free thyroxine; TSH = thyroid-stimulating hormone; TSI = thyroid-stimulating immunoglobulin Methods: We report a case of thyrotoxicosis alternating with hypothyroidism in a 44-year-old, African-American woman and detail the clinical course and management. Results: The patient presented in a mildly thyrotoxic state with features of thyroiditis that resolved soon thereafter. Subsequently, the course shifted toward a hypothyroid state with a thyroid-stimulating hormone (TSH) level of 24.53 μIU/ml (normal range is 0.45 to 4.5 μIU/ml; measured September 5, 2013) and free thyroxine (FT4) of 0.35 ng/dL (normal range is 0.5 to 1.40 ng/dL; measured September 5, 2013). It ensued with alternating hypothyroid and hyperthyroid trajectories for several cycles. Clinical management was adjusted to negotiate each progression. During certain intervals, levothyroxine was increased. At other visits, it was decreased. Periods without medication were observed as well. Furthermore, methimazole and metoprolol were utilized when required. Reversal of the condition occurred repeatedly. The entire course is tracked with over 30 instances of thyroid function measures that included hypothyroid, euthyroid (TSH at 1.54 μIU/mL, FT4 at 1.16 ng/dL) and thyrotoxic states (TSH at <0.005 μIU/mL, FT4 at 2.67 ng/dL). Various antibody titers were elevated including thyroid-stimulating immunoglobulin, thyroid peroxidase antibody, and TSH receptor antibody. Close monitoring of TSH and FT4 allowed for appropriate medication dose adjustment. Conclusion: This case highlights the unusual phenomenon of fluctuating thyroid function with autoimmune involvement of thyroid-stimulating immunoglobulin and TSH receptor antibodies. Close follow up aided responsive clinical management throughout the fluctuating clinical course.