Is It T3 Thyrotoxicosis? A Case of Falsely Elevated Tri-Iodothyronine (T3) Levels Leading to a Diagnosis of Multiple Myeloma

Abstract

We are presenting a case of falsely elevated T3 levels in a patient due to interference from monoclonal immunoglobulins. A 56-year-old, clinically euthyroid man referred to the endocrinology clinic of the Aga Khan university, Karachi Pakistan, for possible T3 thyrotoxicosis after thyroid function tests revealed total T3 >12.32 nmol/L (reference range 0.6–2.79), normal TSH, and total T4 level. There was a mismatch in clinical and laboratory parameters and preliminary laboratory results were suggestive of thyroid binding globulin abnormalities. Further evaluation in this context unmasked multiple myeloma. The presence of monoclonal immunoglobulins can lead to assay interference and spurious results. To the best of our knowledge, this is the second case defining the cause of falsely elevated T3 levels, due to assay interferences with binding of T3 only to monoclonal immunoglobulins.

Elevation of free triiodothyronine (fT3) levels by Plasmodium falciparum independent of thyroid stimulating hormone (TSH) in children with uncomplicated malaria

“… 44 In contrast to publication by, 41 the mean level of fT3 observed in the malaria cases was above the normal Ghanaian level of 2.73–4.13 pmol/L. 45 In isolated fT3 thyrotoxicosis, fatigue, lethargy, and weight loss have been reported, 46 clinical presentations that are commonly observed in about 74% of children with malaria. 5 However, it is not clear whether these symptoms observed in malaria cases could be attributed to elevated fT3.…”

Factitiously Elevated Total Triiodothyronine in a Euthyroid Patient with Multiple Myeloma

“…Ram et al [ 5 ] reported another case of factitious isolated TT3 elevation. Here, a 56-year-old man was investigated for a TT3 reported to be extremely high at 800 ng/dL (39–181) while TT4 and free T3 (FT3) were normal.…”

The Association Between Low T3 Syndrome and Survival in Patients With Newly Diagnosed Multiple Myeloma: A Retrospective Study

“…The normal concentrations of FT3, FT4, and TSH were 2.3 to 4.2 pg/mL, 0.89 to 1.76 ng/Dl, and 0.55 to 4.78 μIU/mL, respectively, in this study. Because the total thyroid hormone in MM patients has been spuriously elevated in previous studies, [23][24][25] we did not include total T3 (TT3) and total T4 (TT4) for analyses in this study.…”