Hypothyroidism in association with systemic amyloidosis

Background. Systemic amyloidosis leads to functional compromise of various organs through infiltration of these tissues by amyloid protein. The majority of affected patients develop infiltration of the thyroid gland; yet thyroid dysfunction rarely occurs. Methods and Results. Described herein is a case of hypothyroidism occurring in a patient with amyloid goiter. An alternative explanation for her hypothyroidism could not be determined by histologic or serologic evaluation. Hormonal assays were consistent with progressive hypothyroidism in spite of oral and, finally, parenteral replacement therapy. A review of the literature describes other cases of thyroid dysfunction reported in patients with systemic amyloidosis. Conclusions. This case illustrates how amyloid infiltration may be a cause of hypothyroidism in patients with systemic amyloidosis. Therefore, all patients who develop a goiter, including those with systemic amyloidosis, must be screened for thyroid dysfunction. When a physician diagnoses the patient with hypothyroidism, that physician must be aware of potential pitfalls in the administration of thyroxine replacement as outlined below.