Abstract #1397146: Recurrent Thyrotoxicosis in a Woman with a History of Graves - Basedow Disease

Abstract

Although the most common cause of thyrotoxicosis is Graves - Basedow disease (GBD), the determination of the cause of thyrotoxicosis is important for establishing appropriate management. We present the case of a woman with suspected surreptitious ingestion of thyroid hormones or factitious thyrotoxicosis. A 42-year-old female patient she was diagnosed with hyperthyroidism due to GBD at the age of 14. At age 17 she received RAI (10 mCi), developed hypothyroidism and started levothyroxine (L-T4). At age 38 she presented again with hyperthyroidism: TSH: < 0.004 uIU/mL (VN: 0.4-4) and FT4: 3.19 ng/dl (0.8-1.9). She was suspended L-T4 and started antithyroid drugs (thiamazole). Due to persistence of hyperthyroidism despite 40 mg/d of thiamazole. She was hospitalized for study; thyroid ultrasound showed an atrophic thyroid and thyroid scintigraphy with technetium-99m reported absence of uptake in the thyroid bed, Ab-TPO and Ab-Tg were negative, Thyroglobulin: <0.2 ng/ml (1.6-59.9). After discontinuation of thiamazole and without any other medication, thyroid hormones (FT4 and FT3) normalized within two weeks, factitious thyrotoxicosis was suspected, and she was discharged without medication. At 42 years of age, she returned due to hyperthyroidism with TSH: 0.004uIU/mL, FT4: 2.59 ng/dl, and FT3: 5.05 pg/ml despite having restarted thiamazole in her place of origin; she denied taking thyroid hormone or nutritional supplements. On examination: HR: 105 bpm, mild distal tremor and non-palpable thyroid. The results of the thyroid, thyroid scintigraphy, Ab-TPO, Ab-Tg and levels of Thyroglobulin were similar to the previous ones. Transvaginal ultrasonography and a whole-body scan with RAI ruled out ectopic hyperthyroidism; the FT3/FT4 ratio was always less than 4.4, suggesting factitious thyrotoxicosis. Antithyroid and beta-blockers were suspended, control at 48 hours showed: FT4: 1.77ng/dl (0.8-1.9), FT3: 3.4pg/ml (1.8-4.2) and 25 days post-discharge: TSH: 7.72 ng/dl, FT4: 1.48 ng/dl and FT3: 2.09 pg/ml. The psychiatric evaluation did not show any alteration. The patient was asymptomatic and returned to her place of origin. Cholestyramine was not accepted by the patient. Factitious thyrotoxicosis is difficult to identify, especially when dealing with a patient with a history of GBD. The diagnosis of factitious thyrotoxicosis is based upon the absence of goiter, suppressed serum Tg level, decreased radioactive iodine (RAI) uptake, and excellent response after cholestyramine treatment in cases in which this entity is suspected.