Abstract
BackgroundDue to the alarming increase in the incidence of thyroid cancer worldwide, more patients are receiving postoperative radioactive iodine (RAI) therapy and these patients are given a low-iodine diet along with levothyroxine withdrawal to induce a hypothyroid state to maximize the uptake of RAI by thyroid tissues. Recently, the reported cases of patients suffering from life-threatening severe hyponatremia following postoperative RAI therapy have increased. This study aimed to systematically assess risk factors for developing hyponatremia following RAI therapy in post-thyroidectomy patients.MethodsWe reviewed the medical records of all thyroid cancer patients who underwent thyroidectomy and postoperative RAI therapy from July 2009 to February 2012. Demographic and biochemical parameters including serum sodium and thyroid function tests were assessed along with medication history.ResultsA total of 2229 patients (47.0±11.0 years, female 76.3%) were enrolled in the analysis. Three hundred seven patients (13.8%) of all patients developed hyponatremia; 44 patients (2.0%) developed moderate to severe hyponatremia (serum Na+≤130 mEq/L) and another 263 (11.8%) patients showed mild hyponatremia (130 mEq/L<serum Na+≤135 mEq/L). In univariate analysis, old age, female sex, presence of hypertension, presence of diabetes, use of thiazide diuretics, use of angiotensin receptor blocker or angiotensin-converting enzyme inhibitors, lung metastasis, and hyponatremia and lower estimated glomerular filtration rate at the start of RAI therapy were significantly associated with hyponatremia in patients undergoing RAI therapy after total thyroidectomy. Multivariate analysis showed that old age, female sex, use of thiazide diuretics, and hyponatremia at the initiation of RAI therapy were independent risk factors for the development of hyponatremia.ConclusionOur data suggest that age greater than 60 years, female sex, use of thiazide, and hyponatremia at the initiation of RAI therapy are important risk factors for developing hyponatremia following RAI therapy in post-thyroidectomy patients.
Highlights
In the last decades, the incidence of thyroid cancer has increased at an alarming rate worldwide [1]
Study population Data for a total of 2241 Differentiated thyroid cancer (DTC) patients who consecutively underwent bilateral total thyroidectomy with central compartment neck dissection and radioactive iodine (RAI) therapy at Gangnam Severance hospital were collected from July 2009 to February 2012
After we identified baseline characteristics of all the patients, we divided them into three groups according to the serum sodium level as follows: (1) the moderate to severe hyponatremia group, in which the lowest serum sodium level within seven days after RAI therapy was less than 130 mEq/L (n = 44, 2.0%), (2) the mild hyponatremia group, in which the serum sodium level was 131,135 mEq/L (n = 263, 11.8%), and (3) the normonatremic group, in which the lowest serum sodium level within seven days after RAI therapy was more than 136 mEq/L (n = 1922, 86.2%)
Summary
The incidence of thyroid cancer has increased at an alarming rate worldwide [1]. Many centers use treatment protocols that include thyroid hormone withdrawal and 2–4 weeks of a low-iodine diet prior to RAI therapy to minimize dietary iodine interference and induce hypothyroid status for facilitating the uptake of RAI [3]. Iatrogenic hypothyroid status induced by such treatment protocol may impair water excretion and cause mild hyponatremia Such a lowiodine diet protocol is frequently accompanied by low dietary salt intake. These patients are encouraged to increase oral fluid intake during RAI therapy to flush out the iodine. Due to the alarming increase in the incidence of thyroid cancer worldwide, more patients are receiving postoperative radioactive iodine (RAI) therapy and these patients are given a low-iodine diet along with levothyroxine withdrawal to induce a hypothyroid state to maximize the uptake of RAI by thyroid tissues. This study aimed to systematically assess risk factors for developing hyponatremia following RAI therapy in post-thyroidectomy patients
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