Endocrine Abstracts

Introduction: Factitious thyrotoxicosis is caused by intentional and surreptitious ingestion of thyroid hormone and can be a challenge in the differential diagnosis with other pathologies.

Case report: Female, 35 years old, referred to our department for suspected subacute thyroiditis after COVID-19. The patient had previous medical history of hysterectomy, bilateral oophorectomy, 2 galactophorectomies with right breast reconstruction, depressive syndrome and hypothyroidism medicated with levothyroxine 75 mg since 2016. In March 2021, two months after SARS-CoV-2 infection, she noticed increased cervical volume with associated pain and weight loss of 10 kg. Thyrotoxicosis was identified and thyroid scintigraphy showed diffuse low uptake, suggestive of subacute thyroiditis. Levothyroxine was suspended and she was medicated with 20 mg prednisolone. After 4 months she maintained thyrotoxicosis with no response to therapy, and a total thyroidectomy was suggested by her medical team, being referred to our department. Upon observation, she complained of tiredness and drowsiness, had no signs of thyrotoxicosis and thyroid examination was normal and painless. The patient expressed a desire to undergo surgery to control the symptoms. At that time, under prednisolone 20 mg, analytical evaluation showed: TSH <0.005 uU/ml, FT4 6.25 ng/ml (0.97-1.58), FT3 18.8 pg/ml (2.38-4.37), thyroglobulin 2.4 ng/ml, negative TRAB, TG and TPO antibodies, AST 46 IU/l (7-32), ALT 73 IU/l (7-32). Thyroid scintigraphy was repeated and showed diffuse low uptake. Due to suspected factitious thyrotoxicosis, it was decided to admit the patient and without instituting any therapy a clear improvement in thyroid function was observed after 5 days: TSH <0.008, FT4 1.11 (0.97-1.48), FT3 3.70 (1.88-3.18). When confronted with the results and after being evaluated by Psychiatry, the patient denied intentionally taking levothyroxine.

Discussion: In the presented case, the suspicion of factitious thyrotoxicosis was based on the absence of goiter, low level of thyroglobulin, low uptake on thyroid scintigraphy and persistence of thyrotoxicosis six months after the diagnosis of subacute thyroiditis. The suspicion was confirmed by the rapid decrease in the serum value of thyroid hormones (50% FT4 and 41% FT3) without any therapy.

Conclusion: This case reflects the importance of clinical suspicion and timely diagnosis of factitious thyrotoxicosis, avoiding unnecessary and potentially invasive treatments.