Disorders of sodium balance: Hypothyroidism and hyponatraemia: an old wives' tale?

doi:10.1136/bmj.332.7545.854

BMJ 2006;332:854 (8 April), doi:10.1136/bmj.332.7545.854

Letter

Disorders of sodium balance

Hypothyroidism and hyponatraemia: an old wives' tale?

The first 150 words of the full text of this article appear below.

EDITOR—Like many other sources, Reynolds et al includehypothyroidism as a secondary cause of hyponatraemia.¹ However,the evidence supporting this association is extremely poor.Studies in babies with severe congenital hypothyroidism havefound no change in serum sodium concentrations after treatmentwith levothyroxine.² This has repeatedly been found to be thecase in adults too.^{3 4} A study performed by our group foundno difference in sodium concentrations between 999 patientswith a new diagnosis of hypothyroidism from their family doctorand 4875 controls with normal thyroid function.⁵ Indeed, noneof the hypothyroid patients had a serum sodium concentration< 120 mmol/l at diagnosis, while this was present in twoof the controls.

Credit: FRANCIS LEROY/BIOCOSMOS/SPL

Hypothyroidism is a common condition, and so is hyponatraemiain acutely unwell patients admitted to hospital. However, whenhyponatraemia and hypothyroidism are found to co-exist, thehyponatraemia is not necessarily a consequence of . . . [Full text of this article]

Eric S Kilpatrick, consultant in chemical pathology

Hull Royal Infirmary, Hull HU3 2JZ Eric.Kilpatrick@hey.nhs.uk