FRI569 A Therapeutic Dilemma: Spontaneous Oscillating Graves' Disease And Hypothyroidism

Abstract

Abstract Disclosure: D. Suravajjala: None. J. Case: None. S. Kolli: None. V. Eranki: None. Spontaneous recurrent conversions between hyperthyroidism and hypothyroidism in Graves’ disease (GD) is very rare. We present a case of GD with spontaneous oscillation since diagnosis. From our review, less than 10 cases have been reported in the literature with alternating hyper and hypothyroidism. The patient is a 68-year-old female diagnosed with GD 4 years back with TSH <0.01 (0.4 - 4.5 uIU/mL) and TSI 25.70 (0.00-0.5 IU/L). She denied viral illness, radiation exposure, Lithium or Amiodarone use. Ultrasound thyroid was consistent with GD. Thyroid uptake scan was also consistent with GD. Eventually, Methimazole (MMI) 10 mg daily was initiated. About five months after MMI treatment, she was found to be hypothyroid with TSH 9.030 (0.4-4.5 uIU/mL) and FT4 0.99 (0.9-2.2 ng/dl) which led to discontinuation of MMI. 2 months later, she was clinically hyperthyroid with TSH 0.026, FT4 2.93 (0.9-2.2 ng/dl), TSI 9.59 (0-0.55 IU/L). MMI 5 mg daily was resumed, and as she preferred medical management, other treatment options for GD were not considered. Six months after low dose MMI, patient again reverted to hypothyroidism with TSH 21.420, FT4 0.82. MMI 5 mg was changed to every other day. After 8 months, she was found to be clinically and biochemically hypothyroid with TSH 147, FT4 0.41 (0.9-2.2 ng/dl), TSI 7.98 (0-0.55 IU/L). With the suspicion that she had burnt out GD, she was started on Levothyroxine (LT4) 100 mcg daily. Two months after LT4 initiation, she became clinically hyperthyroid with TSH 0.010 (0.4-4.5 uIU/mL) and FT4 1.91 (0.9-2.2 ng/dl). When trial of LT4 dose reduction failed to alleviate patient hyperthyroid symptoms, it was discontinued and MMI was resumed at 2.5 mg qd. Within 3 months she reverted to hypothyroidism. HAMA interference was as well ruled out. Although the patient's thyroid function ranged spontaneously from hyperthyroidism to hypothyroidism, she was still reluctant for definitive treatment options for GD, including RAI ablation and total thyroidectomy. As GD patients may have definitive treatment early, spontaneous conversion between hyperthyroidism and hypothyroidism is usually not seen in GD and most episodes usually occur several years after discontinuation of antithyroid drugs. It is known that both TSH receptor stimulating antibodies (TSAb) and TSH receptor blocking antibodies (TBAb) can be produced at the same time. The presence of hyper or hypothyroidism may depend on the equilibrium between stimulating and blocking antibodies. Switching of TSH receptor antibodies between stimulation and blockage is uncommon. Diagnosis demands careful clinical and biochemical assessments. Alternatively, the case may be easily mistaken for excessive thyroid suppression or replacement. This condition is difficult to manage, and definitive treatment options could be considered with I-131 ablation, thyroidectomy, or pharmacological treatment (block and replace). Presentation: Friday, June 16, 2023