Severe hyponatremia and Schmidt's syndrome

Area of Science:

• Endocrinology
• Autoimmune Diseases
• Internal Medicine

Background:

• Schmidt's syndrome, also known as autoimmune polyendocrine syndrome type 2, involves adrenal insufficiency and autoimmune thyroid disease.
• Severe hyponatremia, defined as serum sodium <115 meq/l, is a rare but serious complication.
• Previous reports suggest a link between severe hyponatremia and hypothyroidism in Schmidt's syndrome.

Observation:

• A 43-year-old woman presented with severe hyponatremia.
• The patient was diagnosed with Schmidt's syndrome during the diagnostic workup.
• This case is unique as it presents with normal thyroid function tests and normal baseline cortisol levels.

Findings:

• A comprehensive literature review identified only seven reported cases of severe hyponatremia associated with Schmidt's syndrome, including this case.
• Severe hypothyroidism appears to be a more common co-occurrence with severe hyponatremia in Schmidt's syndrome.
• This report details the first instance of severe hyponatremia in Schmidt's syndrome occurring with normal thyroid function and baseline cortisol.

Implications:

• The findings suggest that severe hyponatremia can occur in Schmidt's syndrome even without overt hypothyroidism or significantly impaired baseline cortisol.
• This broadens the clinical spectrum and diagnostic considerations for patients presenting with severe hyponatremia.
• Further research is warranted to elucidate the precise mechanisms linking hyponatremia to Schmidt's syndrome, particularly in euthyroid and normocortisolemic states.