Mean pre-isolation sodium concentration was Mean post-isolation sodium concentration was There was significant difference between pre- and post-isolation sodium concentrations with a mean difference of 1. Post-isolation, mild hyponatremia was present in 18 patients 8. Data of these 22 patients are summarized in Table 1. Sodium concentration while on thyroxine treatment documented by simultaneous suppressed TSH concentration were available in 21 patients within 4 to 12 mean 7.
All were within the normal range. None of the patient complained of nausea or symptoms of hyponatremia.
We divided the study sample into two subgroups according to mean age. Risk factors for hyponatremia. As shown in Figure 2 , pre-post isolation drop in sodium concentration was significantly more in females mean difference 1.
However, females had significantly lower creatinine concentration mean difference Comparison of pre- post-isolation drop in sodium concentration between acutely hypothyroid males and females undergoing radioiodine treatment. Data represent mean SD. Pre- post-isolation drop in sodium concentration was significantly more in females than in 43 males mean difference 1.
We have previously reported in a retrospective study [ 2 ] that the mean drop in sodium concentration from the euthyroid state to acute severe hypothyroid state is only 1.
A more recent retrospective study on a large number of newly diagnosed hypothyroid patients median age 64 years, severity of hypothyroidism not reported found no clinically relevant association between newly diagnosed hypothyroidism and hyponatremia [ 15 ].
Few case report studies [ 12 — 14 ] have addressed hyponatremia in the setting of acute hypothyroidism and radioiodine treatment that typically involve low salt diet and excess fluid intake and possibly anxiety and nausea.
In another study, two patients who were placed on low iodine diet in preparation for testing and possible treatment with radioiodine developed severe hyponatremia that required hospitalization [ 13 ]. All our patients were given verbal and written instructions by a designated thyroid cancer coordinator to follow a low-salt, low-iodine diet. However, we have not confirmed their compliance by measuring urine or serum iodine concentrations.
Nevertheless, the current study indicates that the incidence of hyponatremia in acute uncomplicated hypothyroidism even when associated with increased fluid intake, anxiety, and nausea is low. Our finding that acute hypothyroidism is not associated with hyponatremia is supported by the observation that there was no correlation between pos-isolation sodium concentration on one hand and TSH concentration or fluid intake on the other.
Interestingly, we found significantly more drop in sodium concentration pre- post-isolation in females than in males. Despite having similar age, severity of hypothyroidism, pre-isolation sodium concentration, and fluid intake, females experienced larger drop in sodium concentration in association with radioiodine treatment and increased fluid intake. This is consistent with some [ 15 , 16 ] but not all [ 17 ] of the literature showing a preference of hyponatremia for female gender and gender related differences in antidiuretic response to desmopressin [ 18 ] that may be related to increased expression of vasopressin V2 receptor in females [ 19 ].
In addition, we have identified the following risk factors for hypothyroidism associated lowering of sodium concentration, age, elevated creatinine concentration, and diuretics use. Age has been shown to be an independent risk factor for hyponatremia [ 15 , 17 ], carbamazepine-induced hyponatremia [ 20 ], and thiazide-induced hyponatremia [ 21 ]. The mechanisms by which hypothyroidism may induce hyponatremia include an inability to maximally suppress antidiuretic hormone [ 4 , 22 , 23 ] and decreased glomerular filtration that can directly diminish free water excretion by diminishing water delivery to the diluting segments [ 3 , 5 , 6 , 22 , 24 ].
Since hyponatremia did not occur in our patients despite increased water intake, it appears that the first mechanism may not be implicated in acute hypothyroidism.
Direct measurement of antidiuretic hormone concentration would be required to validate this observation. We conclude that in the setting of acute severe hypothyroidism: 1 clinically-important hyponatremia is uncommon; sodium concentration may not need to be monitored unless patients have impaired renal function or are on diuretics, 2 age and female gender are associated with lower sodium concentration.
The association between clinically-important hyponatremia and hypothyroidism may be restricted to chronic uncorrected hypothyroidism. Rose BD: Hyponatremia in hypothyroidism. Prev Next. Endocrine Abstracts 15 P Author affiliations.
Leighton Hospital, Crewe, UK. Volume 15 Next Prev. Summary Programme Abstracts. Article tools. My recent searches. Competing interests: The authors have declared that no competing interests exist. Hypothyroidism is often referred to as a cause of hyponatremia, but several reports have shown that the association between thyroid function and serum sodium levels is very weak and of marginal clinical relevance[ 1 — 6 ]. Retrospective cross-sectional analyses have shown that the prevalence of hyponatremia and distribution of serum sodium levels were similar among euthyroid and hypothyroid patients[ 1 ].
A recent review and clinical practice guideline for hyponatremia have mentioned that even though hypothyroidism is one possible cause of hyponatremia, it should only be attributed to severe hypothyroidism, as in myxedema coma[ 4 , 6 , 7 ].
However, past reports had simply compared the prevalence of hyponatremia between patients with and without hypothyroidism[ 1 , 5 , 8 ]. In addition, some confounders such as sex, age, kidney function, and serum albumin level, which are reported to be associated with thyroid function[ 9 — 12 ], were not considered.
Furthermore, no information was available about the prevalence of hypothyroidism with varying severity of hyponatremia. The objective of the present retrospective cross-sectional study was to investigate the prevalence of hypothyroidism by severity of hyponatremia, and to clarify whether the association between the severity of hyponatremia and hypothyroidism is affected by confounding factors associated with thyroid function. The study was conducted in accordance with the Declaration of Helsinki.
The ethics committee approved waiver of informed consent for this study. Both are tertiary hospitals in their respective medical districts. For each patient, initial TSH data during the study period and free thyroxine T4 data from the same day were obtained. Patient age, sex, and levels of serum creatinine, blood urea nitrogen, potassium, chloride, total protein, albumin, and free triiodothyronine T3 on the same day as TSH testing were also obtained.
Next, we extracted the minimum serum sodium Na level within 3 days of TSH testing because TSH testing was unavailable at night and during holidays. Consequently, hyponatremia could have already been treated by the time of TSH testing.
We excluded patients aged 17 years or younger. The reference ranges for TSH and free T4 were 0. Continuous variables were expressed as medians and interquartile ranges and compared using the Kruskal-Wallis test. Linear trends in proportions were assessed using the Cochran-Armitage test.
Multivariate models were adjusted for sex, age, eGFR, and serum albumin, which are factors that have previously been reported to be associated with thyroid function[ 9 — 12 , 15 ].
Univariate and multivariate linear trend tests were performed using each Na category as an ordinal variable. Overall, data from 71, patients were included in this study.
Patient characteristics are shown in Table 1. In total, 4, patients 6. The proportion of overt hypothyroidism in the same categories was 1. Among patients with hypothyroidism and overt hypothyroidism, the values were A statistically significant but weak correlation was observed between TSH and Na in the entire study population. No statistically significant relationship was observed between TSH and Na among patients with hypothyroidism and overt hypothyroidism, respectively.
Correlation between thyrotropin and serum sodium levels in all patients a , patients with hypothyroidism b , and overt hypothyroidism c. The unadjusted and adjusted odds ratios for hypothyroidism and overt hypothyroidism in each hyponatremia category are shown in Table 2.
The odds ratios for overt hypothyroidism were 1. This retrospective cross-sectional study investigated the prevalence of hypothyroidism in patients with hyponatremia. Open J Thyroid Res 1 1 : DOI: Main article text. Introduction Hyponatremia is the most common electrolyte abnormality encountered in ambulatory and hospital settings.
Materials and Methods We performed a retrospective chart review of patients presenting to either the ambulatory clinics or in-patient units between September 1, and August 31, Study population Patients who had both serum sodium Na and serum thyrotropin TSH obtained previously were included in the study.
Hyponatremia was defined as serum Na Table 1: Categories of thyroid status and sodium status. Table 2: Patient characteristics. Islander 0. Table 3: Univariable summaries of TSH and sodium overall and within patient status. Table 6: Serum sodium by thyroid state. We are indebted to Dr. Sameera Daud for helping with the design of the study. American Journal of Medicine S Clinical Endocrinology Oxf New England Journal of Medicine Lancet Journal of Endocrinological Investigation Acta Paediatrica,93 1 Endocrine Practice American Journal of Medicine American Family Physician American Journal of Kidney Diseases J Am Soc Nephrol 1: Endocrinology Lancet 2: Journal of the American Society of Nephrology J Hosp Med 6: E This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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