SAT473 First Case Of Diffuse Thyroid Lipomatosis With Amyloid Deposits Presenting With Hyperthyroidism
Authors: Gonzalez Gil Adrian Marcelo , Ruiz Santillan Marco Andres , Quadri Hamza , Force Bahar Kapoor , Gaba Ruchi 
Published: October 2023

Disclosure: A.M. Gonzalez Gil: None. M.A. Ruiz Santillan: None. H. Quadri: None. B.K. Force: None. R. Gaba: None.

Background: Diffuse thyroid lipomatosis (DTL) is an exceedingly rare entity of unknown etiology which can be associated with amyloidosis. It generally presents with euthyroidism but very few cases with hyperthyroidism have been reported. Clinical Case: A 64-year-old woman from Pakistan with a several-year history of a non-tender goiter presented to the emergency department with an upper respiratory and gastrointestinal viral syndrome in the context of several weeks of progressively worsening fatigue. She also reported unintentional weight loss over several years. She denied other hyperthyroid or compressive symptoms. Her exam was notable for resting sinus tachycardia and an approximately 100 gm painless goiter. Laboratory evaluation was notable for a markedly elevated creatinine with nephrotic range proteinuria. She was declared to have end stage renal disease (ESRD) and hemodialysis was initiated. She was also found to have a suppressed TSH (&lt;0.01 uIU/mL, NR=0.45-5.33) and elevated FT4 (2.17 ng/dl, NR=0.64-1.42). Total T3 was low (42 ng/dl, NR=87-178), which was attributed to hypoalbuminemia and altered peripheral thyroid hormone metabolism with underlying ESRD. Further evaluation revealed elevated ESR, CRP and thyroglobulin levels (625.9 ng/mL, NR=1.5-38.5), while thyroid stimulating immunoglobulin, thyroid receptor antibodies and thyroid peroxidase antibodies were undetectable. A thyroid ultrasound revealed an enlarged fatty thyroid consistent with DTL. A radioactive iodine uptake scan revealed normal 24-hour uptake (14.1%, NR=7-32%) in a slightly heterogeneous thyroid with no aberrant functioning thyroid tissue. She was started on atenolol, with significant improvement in her tachycardia, but her FT4 continued to increase. Methimazole was initiated. Dose uptitration and administration after dialysis resulted in near-normalization of FT4 levels. She subsequently underwent renal and thyroid biopsies, both of which showed apple green birefringence under polarized light with Congo Red stain, indicating amyloidosis. Core thyroid biopsy additionally showed benign adipose tissue with entrapped thyroid follicles, confirming concomitant DTL. Although other authors have found thyroid amyloid deposits in DTL, and yet others have reported hyperthyroidism in DTL without amyloidosis, this is the first reported case of hyperthyroidism in a patient with DTL with amyloid deposits. Interestingly, chronic hypoxia in amyloid goiters has been hypothesized to cause fibroblast-to-adipocyte metaplasia leading to DTL. We speculate that excess thyroid hormone release could also be mediated by follicular cells’ response to hypoxia induced by amyloid and fatty infiltration of the thyroid. Conclusion: To the best of our knowledge, this is the first reported case of diffuse thyroid lipomatosis with amyloid deposits to be associated with concurrent hyperthyroidism.

Presentation Date: Saturday, June 17, 2023