SAT-577 Managing Patients with Contrasting Thyroid Dysfunction: Is Definitive Treatment Necessary?

Introduction: Graves Disease (GD) and Hashimoto Thyroiditis (HT) are the most frequent causes of hyper- and hypothyroidism in developed countries. Prevalence in the US has been reported at 1.3% and 4.6% respectively.(1) Concurrent GD-HT is under-diagnosed as data pertaining to this topic is scarce. The purpose of this case report is to describe how a patient with concomitant GD-HT who denied radioactive iodine(RAI)/surgical treatment behaved clinically when receiving prolonged antithyroid drugs (ATD’s) while hyperthyroid-predominant and levothyroxine replacement therapy while hypothyroid-prevalent. Case Presentation: 57 year old female patient evaluated for symptoms of hyperthyroidism, low TSH and normal FT4. New evaluation including a thyroid sonogram and scan, Anti TPO’s, TSI’s, and cytology report revealed a diagnosis of concurrent GD-HT. Patient denied RAI/surgery and started 5mg methimazole (MMI) for 33 months with laboratories oscillating amidst asymptomatic subclinical hyperthyroidism (aSCHy) and euthyroidism (EU) for 33 months. Patient became hypothyroid due to MMI and was discontinued, subsequently developing aSCHy so MMI was restarted and continued for 4 months. Patient remained treatment free the following 34 months when she became hypothyroid and since has been placed on 25mg levothyroxine. Discussion: A study conducted in USA concludes that among patients on thyroid medication, only 60% had normal TSH.(2) Although our patient never achieved EU (defined by two years of normal laboratory values), satisfactory results were attained. Laboratories oscillated between EU and aSCHy without osteoporosis or cardiovascular complications. 2 case series describe GD patients who develop HT after ATD treatment.(3,4) However, it’s not clear whether patients were offered FNA when initially hyperthyroid, therefore not being able to rule-out GD-HT. Our patient had evidence of HT by cytology with normal uptake ruling out hashitoxicosis, and no evidence of Schmidt’s syndrome. Conclusion: A definitive treatment may not always be necessary in patients with concurrent GD-HT and thyroid dysfunction should be analyzed meticulously. Prolonged low doses of MMI and LT4 replacement can be safe and effective in these patients, rendering satisfactory results. References: 1. Hollowell JG, et al. (2002). Serum TSH, T4, and Thyroid Antibodies in the United States Population (1988 to 1994): National Health and Nutrition Examination Survey (NHANES III). J Clin Endocrinol Metab,87(2), 489-99 2. Canaris G, et al. (2000). The Colorado Thyroid Disease Prevalence Study. Arch Intern Med,160(4), 526-34 3. Umar H, et al. (2010). Hashimoto Thyroiditis Following Graves’ Disease. Indones J Intern Med, 42(1), 31-35 4. Smyczńyska J, et al. (2014). Persistent remission of Graves` disease or evolution from Graves' disease to Hashimoto's thyroiditis in childhood. Neuro Endocrinol Lett, 35(5), 335-41