Hypothyroidism and hyponatremia - rather co-incidence than causality.

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Hypothyroidism and hyponatremia - rather co-incidence than causality.

Thyroid. 2017 Mar 28;:

Authors: Wolf P, Beiglböck H, Smajis S, Wrba T, Rasoul-Rockenschaub S, Marculsecu R, Gessl A, Luger A, Winhofer Y, Krebs M

Abstract
BACKGROUND: Hypothyroidism is referred to be a rare, but possible, cause of hyponatremia. However, there is only poor evidence supporting this association. Since hyponatremia and hypothyroidism are both common conditions themselves, we suppose that co-occurrence does not have to be causal.
METHODS: To address a potential relationship we performed a retrospective analysis of data from the Division of Endocrinology of the Medical University of Vienna from 04/2004 to 02/2016. 8053 hypothyroid patients (48±24 years, 71 % female) with thyroid stimulating hormone (TSH) > 4.0 uU/ml and available blood tests for free tetra-iodothyronine (fT4) and sodium (Na+) within maximal +/- seven days were included and screened for hyponatremia. Patients' records were searched for concomitant disease and medication, when sodium concentration was < 135 mmol/l.
RESULTS: Hyponatremia was present in 448 of 8053 patients (5.56 %). Analysis of medical history revealed potential alternative causes of hyponatraemia in 442 of 448 patients (98.88%), i.e. side effects of medication, concomitant underlying disease or other endocrine disorders. This distribution did not differ between patients suffering from clinical or subclinical hypothyroidism. No case of clinically relevant hyponatremia (Na+ < 130 mmol/l), present in 111 of 448 patients (24.78 %), could be attributed only to hypothyroidism. There was a very weak but statistically significant trend towards a positive association between thyroid function and serum sodium levels (Na+/TSH:R=0.022;p=0.046;Na+/fT4:R=-0.047;p<0.001).
DISCUSSION: Our results suggest that hypothyroid patients with moderate to severe hyponatremia often have other potential explanations for their low serum sodium concentrations in routine care.

PMID: 28351291 [PubMed - as supplied by publisher]

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