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Rapid Preoperative Preparation for Severe Hyperthyroid Graves’ Disease

Endocrine Unit, Soroka University Medical Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel 84101

Address correspondence to: Yair Liel, M.D., Department of Medicine, CPO Box 151, Beer-Sheva, Israel 84101. E-mail: liel{at}bgu.ac.il.

To the editor:

Panzer et al. (1) presented an interesting approach for the rapid preoperative preparation of hyperthyroid Graves’ disease patients, using multiple-level blocking of the thyroid hormones’ synthesis-secretion-activation cascade, suggesting that an average 7-d treatment is sufficient to restore euthyroidism in severely thyrotoxic patients. The data presented indicate preoperative normalization of total T₃, whereas total T₄ and free T₄ index remain somewhat increased.

Although the study clearly demonstrates the clinical feasibility and safety of the protocol, I would like to point to a possible pitfall in the definition of euthyroidism in those patients. We (2) have shown that after withdrawal of T₄ replacement in athyreotic patients, the half-life time (t_1/2) of the free thyroid hormones is considerably longer than the t_1/2 of the total T₄ and total T₃ (7 and 0.8 d, respectively). We observed a mean free T₄ t_1/2 of 11 d (range, 8–13 d) and mean free T₃ t_1/2 of 15.5 d (range, 12–19 d). The longer t_1/2 of the free hormones was attributed to release of T₄ from binding proteins and continuous production of T₃ from T₄ in the periphery. Thus, attainment of euthyroidism according to total thyroid hormone measurements may not correspond in time with biochemical euthyroidism according to free hormone measurements. Because the study of Panzer et al. (1) included blocking of T₄ to T₃ conversion, which was not part of our study, the free T₃ t_1/2 in that circumstance may still be different from that observed in our study. It would be interesting to follow up on their study with current free T₄ and free T₃ assays.

An unfortunate practical problem that may impede the current ability to use this protocol is, of course, the withdrawal from the market of oral iodinated radiographic contrast agents.

Received July 1, 2004.

References

1. Panzer C, Beazley R, Braverman L 2004 Rapid preoperative preparation for severe hyperthyroid Graves’ disease. J Clin Endocrinol Metab 89:2142–2144[Abstract/Free Full Text]
2. Liel Y 2002 Preparation for radioactive iodine administration in differentiated thyroid cancer patients. Clin Endocrinol (Oxf) 57:523–527[Medline]

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