Introduction: Syndrome of inappropriate antidiuretic hormone secretion (SIADH), is generally characterized by hyponatremia and hypo-osmolarity.
Objectives: SIADH may develop following some infectious diseases including brucellosis, which regarding the severity of the disease may cause morbidity or mortality.
Patients and Methods: In this case-control study, 110 patients with brucellosis and 110 healthy controls were enrolled. The case group was selected among patients having clinical signs and symptoms of brucellosis with a Wright test titer ≥1/160 and a 2ME test titer ≥1/80. About 10 cc blood sample was taken from each of them to test the blood sugar, thyroid stimulating hormone (TSH), serum sodium, serum potassium, blood urea nitrogen (BUN), creatinine, and serum cortisol. Random urine samples were also taken from participants to measure the urinary osmolarity and sodium.
Results: The frequency of hyponatremia (Na <135 mEq/L) in patients with brucellosis was significantly higher than the control group but there was no significant difference between the groups in the frequency of abnormal urinary sodium (more than 40 mEq/L). Meanwhile, the frequency of abnormal uric acid (less than 4 mg/dL) was significantly higher in patients than the control group. The frequency of abnormal urine osmolarity (above 300 mOsm/kg) was significantly higher in patients than the control group. In total, only 9 out of 110 patients had SIADH with asymptomatic mild hyponatremia and severe hyponatremia was seen only in one patient with prolonged Brucella meningitis.
Conclusion: Based on the defined criteria, 8.2% of brucellosis patients were at the risk of SIADH, but the findings were in favor of asymptomatic SIADH without prominent hyponatremia.