Endocrinol Metab.  2016 Sep;31(3):410-415. 10.3803/EnM.2016.31.3.410.

Prevalence of Hyponatremia in Hypothyroid Patients during Radioactive ¹³¹I Ablation for Differentiated Thyroid Cancer: Single Institution Experience

• Dayrit JC
• Cunanan EC
• Kho SA

• KMID: 2352980
• DOI: http://doi.org/10.3803/EnM.2016.31.3.410

Abstract

BACKGROUND
Hyponatremia developing in hypothyroid patients has been encountered in clinical practice; however, its prevalence has not been well established.
METHODS
Thirty patients diagnosed with differentiated thyroid cancer, rendered hypothyroid after surgery and levothyroxine withdrawal, and who are for radioactive iodine (RAI) ablation were included. Serum sodium concentrations were measured twice, at the time of admission for RAI ablation, and before discharge after increased oral fluid intake. The outcome measures were to determine the prevalence of hyponatremia among hypothyroid patients prior to RAI ablation and after oral hydration post-RAI, and to correlate the serum sodium levels pre-RAI and post-RAI with thyroid-stimulating hormone (TSH) concentration and age.
RESULTS
Thirty patients were included, with ages from 23 to 65 years old (median, 40). Two patients (6.7%) were hyponatremic prior to RAI ablation, and eight patients (26.7%) had mild hyponatremia (130 to 134 mEq/L) after RAI and hydration. There was no significant correlation between TSH levels and serum sodium levels prior to or after RAI. There was also no significant correlation between pre- and post-RAI sodium concentration and age.
CONCLUSIONS
The prevalence of hyponatremia pre-RAI was 6.7%, and 26.7% post-RAI. No significant correlation was noted between TSH concentration and age on pre- or post-RAI sodium concentrations. Routine measurement of serum sodium post-RAI/isolation is still not advised. Measurement of sodium post-RAI may be considered in patients who are elderly, with comorbid conditions or on medications.

Keyword

Hyponatremia; Hypothyroidism; Differentiated thyroid cancer; Radioactive iodine therapy

MeSH Terms

Aged
Humans
Hyponatremia*
Hypothyroidism
Iodine
Outcome Assessment (Health Care)
Prevalence*
Sodium
Thyroid Gland*
Thyroid Neoplasms*
Thyrotropin
Thyroxine
Iodine
Sodium
Thyrotropin
Thyroxine

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