The abnormal secretion of adrenocorticotropic hormone (ACTH) and antidiuretic hormone (ADH) due to damage to the subthalamic-pituitary system leads to increased urinary sodium excretion and increased water reabsorption by the kidneys, resulting in a series of clinical symptoms of neurological impairment due to decreased blood sodium and low blood osmolality, called the syndrome of abnormal secretion of antidiuretic hormone, abbreviated as SIADH. increased secretion of ADH in clinical How to check it? 1. Laboratory tests (1) Serum sodium is generally less than 130 mmo/L. (2) Plasma osmolality <270 mOsm/kgH2O. (3) Urinary osmolality is inappropriately elevated and is greater than blood osmolality when plasma osmolality decreases. (4) Increased urinary sodium excretion >20 mmol/L. (5) Normal or slightly low CO2 binding and low serum chloride. (6) Serum urea nitrogen, creatinine, uric acid, and albumin are often decreased. (7) Elevated plasma and urinary AVP levels, with plasma AVP greater than 1.5 pg/ml (plasma AVP values <0.5 to 1.5 pg/ml at blood osmolality <280 mOsm/kgH2O). (8) Thyroid, liver, kidney, heart and adrenal cortex functions are normal. 2, water load test In the case of hypertonic urine can be used to identify normal people water load can inhibit pituitary AVP release generally when the blood sodium > 125mmol / L can do this test, otherwise there is a risk of inducing water intoxication when the blood sodium is lower than 125mmol / L can first limit the water to make the blood sodium rise before doing. 3, alcohol and phenytoin sodium inhibition test slowly intravenous injection of 95% alcohol 50ml or phenytoin sodium 0.25g, plasma AVP was measured before and after injection. normal people and SIAVP due to hypothalamic regulatory disorders, AVP decreased after injection. AVP does not decrease in patients with SIAVP caused by tumors Improved alcohol suppression test is to drink 20 ml of 3% ethanol per kg body weight within 30 min after morning fasting urination in water loading test, if the water diuresis insufficiency appeared in water loading test can be improved by alcohol test, it means that AVP overproduction is pituitary in nature. 4.Other auxiliary examinations Imaging examination: Papapostolou et al. found that the high-density signal of the pituitary gland disappeared in 7 cases (87.5%) of 8 patients with SIAVP by MRI examination, while the signal was present in 20 cases (87.5%) of 23 non-SIAVP patients in the control group. Therefore, MRI examination is considered to be important for the diagnosis of SIAVP.