Low-dose radioiodine therapy for patients with intermediate- to high-risk differentiated thyroid cancer.

OBJECTIVE: The efficacy of low-dose radioiodine therapy (RIT) for intermediate-risk or high-risk differentiated thyroid cancer (DTC) patients is controversial. Because of the country's shortage of medical facilities for RIT, 1110-MBq RIT for higher risk DTC patients has been performed on an outpatient basis since 2010 in Japan. Herein, we addressed this issue and attempted to determine prognostic factors for the prediction of RIT outcomes. METHODS: We retrospectively analyzed the cases of 119 patients with papillary thyroid cancer who underwent their first RIT with 1110 MBq radioactive iodine (RAI) following a total thyroidectomy, including 65 (54.6%) intermediate-risk and 54 (45.4%) high-risk patients (according to Japan's 2018 clinical practical guidelines for thyroid tumors). Successful ablation was defined when a negative I-131 whole-body scan and thyroglobulin (Tg) < 2 ng/mL were obtained at a diagnostic scan performed 148-560 days (median 261 days) after the first RIT. RESULTS: The overall ablation success rate was 23.4%. Although the ablation success rates of each pretreatment protocol [recombinant human thyroid stimulating hormone and thyroid hormone withdrawal (THW)] did not differ significantly, THW tended to result in a higher success rate than rhTSH. The Tg level at RIT was the only independent powerful predictive factor for successful ablation. The best cut-off value of Tg for predicting unsuccessful ablation was 9 ng/mL. CONCLUSIONS: The ablation success rate was much lower than those of earlier studies; the most plausible reason would be that higher risk DTC patients were included in this study. The low-dose RIT routinely performed in Japan might be inadequate for the achievement of successful ablation. At least for patients with Tg > 9 ng/mL at the first RIT, a higher dose of RAI is recommended.

Mechanism of acid adaptation of a fish living in a pH 3.5 lake.

Despite unfavorable conditions, a single species of fish, Osorezan dace, lives in an extremely acidic lake (pH 3.5) in Osorezan, Aomori, Japan. Physiological studies have established that this fish is able to prevent acidification of its plasma and loss of Na(+). Here we show that these abilities are mainly attributable to the chloride cells of the gill, which are arranged in a follicular structure and contain high concentrations of Na(+)-K(+)-ATPase, carbonic anhydrase II, type 3 Na(+)/H(+) exchanger (NHE3), type 1 Na(+)-HCO(3)(-) cotransporter, and aquaporin-3, all of which are upregulated on acidification. Immunohistochemistry established their chloride cell localization, with NHE3 at the apical surface and the others localized to the basolateral membrane. These results suggest a mechanism by which Osorezan dace adapts to its acidic environment. Most likely, NHE3 on the apical side excretes H(+) in exchange for Na(+), whereas the electrogenic type 1 Na(+)-HCO(3)(-) cotransporter in the basolateral membrane provides HCO(3)(-) for neutralization of plasma using the driving force generated by Na(+)-K(+)-ATPase and carbonic anhydrase II. Increased expression of glutamate dehydrogenase was also observed in various tissues of acid-adapted dace, suggesting a significant role of ammonia and bicarbonate generated by glutamine catabolism.