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April 1989

Assessment of Thyroid Function During High-Dosage Furosemide Therapy

Author Affiliations

Melbourne, Australia

Arch Intern Med. 1989;149(4):973. doi:10.1001/archinte.1989.00390040163045

To the Editor.—In any patient with refractory cardiac failure, it is crucial to rule out hyperthyroidism, but clinical assessment may be extremely difficult, because tachycardia, atrial arrhythmias, muscle wasting, myopathy, and tremor are frequent findings in heart failure per se. Hence, reliance is placed on laboratory assessment of thyroid function. Such patients are generally treated with loop diuretics, sometimes in very high dosage, as advocated in an article in the Archives by Gerlag and van Meijel,1 who provided data on the efficacy of furosemide, up to 2.5 g daily, in a selected group of patients with refractory congestive cardiac failure, many of whom also had renal insufficiency. If such therapy is used, it is important to be aware of effects that will compromise the biochemical assessment of thyroid function.

The effect of high-dose furosemide on laboratory parameters of thyroid function has only recently been recognized.2-4 The changes