Syndrome of inappropriate antidiuretic hormone differential diagnosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Vindhya BellamKonda, M.B.B.S [2]

Overview

Syndrome of inappropriate antidiuretic hormone (SIADH) must be differentiated from other causes of hyponatremia, such as cerebral salt wasting syndrome, adrenal insufficiency, hypopituitarism, and psychogenic polydipsia.

Differentiating Syndrome of Inappropriate Antidiuretic Hormone from other Diseases

SIADH must be differentiated from cerebral salt wasting, adrenal insufficiency, hypopituitarism, hypothyroidism, and psychogenic polydipsia.

Differential Diagnosis	Similar Features	Differentiating Features
SIADH	Excessive release of antidiuretic hormone (ADH or vasopressin)  from the posterior pituitary gland or another source. Hyponatremia Fluid overload Hyponatremia <135 mmol/l Effective serum osmolality < 275 mOsm Urine sodium concentration > 40 mMol/l Plasma uric acid < 200 Absence of edema-inducing diseases, such as heart failure, liver cirrhosis, and nephrotic syndrome Normal adrenal and thyroid function	Weight loss (in case of malignancy) History of head trauma History of medication intake Positive family history
Cerebral salt wasting syndrome	Hyponatremia Urine sodium concentration > 40 mMol/l	Hypovolemia Intracranial diseases, such as: Tumor Trauma Hematoma
Adrenal insufficiency	Hyponatremia	Weight loss Sparse axillary hair Hyperpigmentation Orthostatic hypotension Fever Hypotension Eosinophilia Hyperkalemia Hypoglycemia Morning low plasma cortisol
Hypopituitarism	Hyponatremia	Fatigue Weight loss Decreased libido Decreased appetite Facial puffiness Anemia Infertility Cold intolerance Amenorrhea Inability to lactate in breast feeding women Decreased facial or body hair in men Short stature in children
Psychogenic polydipsia	Fluid overload Hyponatremia	Defect in the hypothalamus Polyuria Polydipsia Confusion Lethargy Psychosis Seizures