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Fibrous tumors can cause consumptive hypothyroidism
The background of the study. Hypothyroidism can
result from rapid degradation of thyroxine (T4) and triiodothyronine
(T3) (consumptive hypothyroidism). This type of hypothyroidism is
caused by increased activity of type 3 iodothyronine deiodinase,
an enzyme that converts T4 to 3,3',5'-triiodothyronine (reverse
T3) and T3 to 3,3'-diiodothyronine (T2), both of which are inactive.
This report describes an adult with consumptive hypothyroidism caused
by a large fibrous tumor.
Case Report. The patient was a 54-year-old man with a history of hypothyroidism who required increasingly high doses of T4. From mid-1999 to early 2001, while taking 200 to 1000 µg daily (usually 600 to 800 µg daily) of T4, he had normal serum free T4 but high serum thyrotropin (TSH) concentrations (10 to 100 mU/L). In 2001 he noted increasing abdominal enlargement. Computed tomographic imaging revealed a large abdominal mass. The mass was surgically removed; pathological examination revealed a malignant fibrous tumor.
While taking 800 µg of T4 daily before surgery, his serum TSH concentration was 20 mU/L. A few days after surgery he had onset of symptoms of hyperthyroidism and his serum TSH concentration was low (0.09 mU/L). The dose of T4 was reduced, after which his symptoms subsided.
The tumor contained a large amount of type 3 deiodinase activity.
The conclusions of the study. Large tumors composed largely of fibrous tissue may cause consumptive hypothyroidism.
The original article. Ruppe MD, Huang SA, Jan de Beur SM. Consumptive hypothyroidism caused by paraneoplastic production of type 3 iodothyronine deiodinase. Thyroid 2005;15:1369-72.
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| Thyroid Digest Index | | | March 2006 Thyroid Digest |
