Unexpected effect of furosemide on radioiodine urinary excretion in patients with differentiated thyroid carcinomas treated with iodine 131

Impact of Moderate Sodium Restriction and Hydrochlorothiazide on Iodine Excretion in Diabetic Kidney Disease: Data from a Randomized Cross-Over Trial

Sodium restriction may potentially reduce iodine intake. This study aimed to determine the effect of sodium restriction (dietary counseling) on 24-h urinary iodine excretion. Diuretics provide an alternative to sodium restriction and are frequently added to sodium restriction, so the effects of hydrochlorothiazide (50 mg daily) and combined therapy were also studied. We performed a post-hoc analysis of a Dutch multi-center, randomized cross-over trial in 45 patients with diabetic kidney disease with a mean age of 65 ± 9 years, mean eGFR of 65 ± 27 mL/min/1.73 m², median albuminuria of 648 [230–2008] mg/24 h and 84% were male. During regular sodium intake with placebo, mean 24 h urinary sodium and iodine excretion were 224 ± 76 mmol/24 h and 252 ± 94 ug/24 h, respectively (r = 0.52, p < 0.001). Mean iodine excretion did not change significantly if sodium restriction and hydrochlorothiazide were applied separately; mean difference −8 ug/day (95% CI −38, 22; p = 0.6) and 14 ug/day (95% CI −24, 52; p = 0.5), respectively. Combined therapy induced a significant decrease in mean iodine excretion (−37 ug/day; 95% CI −67, −7; p = 0.02), yet this was not seen to a clinically meaningful level. The number of patients with an estimated intake below recommended daily allowances did not differ significantly between the four treatment periods (p = 0.3). These findings show that sodium restriction is not a risk factor for iodine deficiency.

Iodine Status of New Zealand Elderly Residents in Long-Term Residential Care

In response to the re-emergence of iodine deficiency in New Zealand, in 2009 the government mandated that all commercially made breads be fortified with iodized salt. There has been no evaluation of the impact of the program on iodine status of the elderly, despite this population group being vulnerable to iodine deficiency or excess. The aim of this study was to describe the iodine status of elderly New Zealanders in residential aged-care homes following the implementation of the bread fortification program. A cross-sectional survey was conducted, involving 309 residents (median age 85 years) from 16 aged-care homes throughout NZ. Information on socio-demographic, anthropometric, dietary and health characteristics were collected. Casual spot urine samples were analysed for urinary iodine concentration (UIC). Blood samples were analysed for serum thyroglobulin, thyroglobulin antibodies, and other biochemical indices. The median UIC (MUIC) of the residents was 72 μg/L, indicating mild iodine deficiency, and 29% had a UIC < 50 μg/L. Median thyroglobulin concentration was 18 ng/mL and 26% had elevated thyroglobulin concentration (>40 ng/mL), suggesting iodine insufficiency. Diuretic use was associated with lower MUIC (p = 0.043). Synthetic thyroxine use was associated with lower odds of having a UIC < 50 μg/L (OR 0.32, p = 0.030)) and lower median thyroglobulin (−15.2 ng/mL, p = 0.001), compared with untreated participants. Frailty was associated with elevated thyroglobulin (p = 0.029), whereas anemia was associated with lower thyroglobulin (p = 0.016). Iodine insufficiency persists in New Zealanders residing in residential aged-care homes despite increasing iodine intake from fortified bread. Research is required to establish optimal iodine intake and status in the elderly.

Radioiodine therapy in benign thyroid diseases: effects, side effects, and factors affecting therapeutic outcome

Radioiodine ((131)I) therapy of benign thyroid diseases was introduced 70 yr ago, and the patients treated since then are probably numbered in the millions. Fifty to 90% of hyperthyroid patients are cured within 1 yr after (131)I therapy. With longer follow-up, permanent hypothyroidism seems inevitable in Graves' disease, whereas this risk is much lower when treating toxic nodular goiter. The side effect causing most concern is the potential induction of ophthalmopathy in predisposed individuals. The response to (131)I therapy is to some extent related to the radiation dose. However, calculation of an exact thyroid dose is error-prone due to imprecise measurement of the (131)I biokinetics, and the importance of internal dosimetric factors, such as the thyroid follicle size, is probably underestimated. Besides these obstacles, several potential confounders interfere with the efficacy of (131)I therapy, and they may even interact mutually and counteract each other. Numerous studies have evaluated the effect of (131)I therapy, but results have been conflicting due to differences in design, sample size, patient selection, and dose calculation. It seems clear that no single factor reliably predicts the outcome from (131)I therapy. The individual radiosensitivity, still poorly defined and impossible to quantify, may be a major determinant of the outcome from (131)I therapy. Above all, the impact of (131)I therapy relies on the iodine-concentrating ability of the thyroid gland. The thyroid (131)I uptake (or retention) can be stimulated in several ways, including dietary iodine restriction and use of lithium. In particular, recombinant human thyrotropin has gained interest because this compound significantly amplifies the effect of (131)I therapy in patients with nontoxic nodular goiter.

Radioactive iodine-refractory differentiated thyroid cancer: unmet needs and future directions

Approximately 90% of thyroid cancers are differentiated (DTCs) and have papillary, follicular or Hürthle cell morphology. Although treatment with surgery and radioactive iodine (I-131; RAI), as appropriate, is associated with significant cure rates and survival benefits, clonal disease progression with development of refractoriness to RAI poses a major therapeutic challenge in about 15% of patients. Traditional chemotherapeutic agents are relatively ineffective and are associated with significant toxicities. Molecular studies have demonstrated that the development and progression of DTC are associated with a series of consistent abnormalities in pathways such as MAPK/ERK and PI3/Akt, which govern cellular growth, proliferation, apoptosis and angiogenesis. Small molecular inhibitors that target these pathogenic pathways, without many of the impairments associated with cytotoxic chemotherapy, have demonstrated efficacy in a variety of malignancies, including renal cell carcinoma, hepatocellular carcinoma, non-small-cell lung cancer and chronic myelogenous leukemia. Several targeted therapeutic agents are in development for the treatment of RAI-refractory DTC. Sorafenib and lenvatinib are being studied in placebo-controlled Phase III trials based on encouraging efficacy results observed in single-arm Phase II studies.

Estimation of the Release Time from Isolation for Patients with Differentiated Thyroid Cancer Treated with High-dose I-131

PURPOSE

Patients receiving high-dose I-131 to treat differentiated thyroid cancer are isolated from visitors to limit radiation exposure to reasonable levels. The appropriate isolation time is unclear and has not been reported in Korea. The purpose of this study was to estimate the isolation time and investigate the possibility of earlier release from isolation.

METHODS

This study was a retrospective analysis of data from 71 patients (10 men and 61 women; mean age, 49 ± 11.1 y) who received 3.7 GBq (47 patients), 5.55 GBq (23 patients), or 7.4 GBq (1 patient) of I-131 between January 2008 and December 2008. The radiation dose was measured with a fixed probe placed inside the isolation room. The total estimated dose equivalent (TEDE) to family members, the time required for the external dose rate to become <0.07 mSv/h, and the time required for whole-body retention to become <1.2 GBq were calculated.

RESULTS

By the TEDE criterion (<5 mSv), 70 of 71 patients (98.6%) could have been released without isolation. By the external dose rate criterion, 10 of 71 (14.1%) and 60 of 71 patients (84.5%) could have been released without isolation and within 24 h, respectively. With whole-body retention criterion, 19 of 71 (26.8%) and 48 of 71 patients (67.6%) could have been released within 24 h and within 48 h, respectively.

CONCLUSIONS

Appropriate release times were estimated and compared using different criteria. Most patients could have been released without isolation or within 24 h of radiation treatment.