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

BackgroundHyponatremia developing in hypothyroid patients has been encountered in clinical practice; however, its prevalence has not been well established.MethodsThirty 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.ResultsThirty 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.ConclusionsThe 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

Validation of the UST thyroid scoring index against ultrasensitive assays for thyroid-stimulating hormone and free thyroxine

Background: Clinical manifestations of thyroid dysfunction are variable. The UST Scoring Index for thyroid disorders, formulated in the 1990s to evaluate thyroid functional status, was based on total thyroid hormone levels and thyroidal iodine uptake. However, with the advent of newer and more sensitive tests, the recommendations and practice now dictate the use of thyrotropin (TSH) and free thyroxine (FT4) levels in the confirmation of thyroid dysfunction. Objective: To validate the UST Scoring Index for thyroid disorders using TSH and FT4. Methods/Results: The UST Clinical Scoring Index was administered to 170 patients presenting for thyroid-related complaints. Thyroid function tests were then requested (TSH and Free T4) and they were classified according to biochemical status. We obtained the following: 43 hyperthyroid, 102 euthyroid and 25 hypothyroid subjects. The mean TSH for the 3 groups were 0.08, 1.28, and 41.50 uIU/mL respectively (NV 0.27-3.75.) Mean FT4 levels were 36.18, 18.33, and 8.43 pM/L respectively (NV 10.3-25.0.) The most frequent findings in the biochemically hyperthyroid group were thyroid enlargement (88%), easy tiredness (74%), palpitations (70%), and nervousness (65%); in the euthyroid group, easy tiredness (62%), thyroid enlargement (54%), palpitations (53%), and irritability (49%); in the hypothyroid group, easy tiredness (64%), exertional dyspnea (52%), weight gain (44%), and constipation (44%.) The UST scoring index for thyroid disorders has a sensitivity of 67%, specificity of 84%, and accuracy rate of 80%, with AUC of 0.850 on ROC analysis for the detection of hyperthyroidism. For detecting hypothyroidism, it has a sensitivity of 40%, specificity of 92%, and asccuracy rate of 85%, with AUC 0.7553 on ROC analysis. Conclusion: The UST scoring index for thyroid disorders has good sensitivity, specificity and accuracy rate based on ROC when validated using TSH and FT4 for the detection of hyperthyroidism and hypothyroidism