SIADH (Syndrome Of Inappropriate ADH)

Syndrome of Inappropriate Antidiuretic Hormone (SIADH) is a condition in which the body produces or releases too much antidiuretic hormone (ADH). Normally, ADH helps regulate water balance by controlling how much water the kidneys reabsorb. In SIADH, excessive ADH leads to water retention, dilution of blood sodium (hyponatremia), and disturbances in fluid balance.

The hallmark feature of SIADH is low sodium levels in the blood, which can cause symptoms such as nausea, headache, muscle cramps, confusion, irritability, and in severe cases, seizures or coma. Unlike diabetes insipidus, which causes excessive urination, SIADH results in concentrated urine and reduced urine output despite fluid overload.

Causes of SIADH include brain injuries, infections, certain cancers (especially lung cancer), and medications such as antidepressants or chemotherapy drugs. Diagnosis involves blood and urine tests to measure sodium concentration and osmolality, along with ruling out other causes of hyponatremia.

Treatment focuses on correcting sodium imbalance and managing the underlying cause. Fluid restriction is often the first step, while severe cases may require medications that block ADH effects or careful sodium replacement. Early recognition and management are crucial, as untreated SIADH can lead to dangerous neurological complications.