Antidiuretic Hormone

Test Description

Antidiuretic hormone (ADH), originally known as vasopressin, is a hormone produced

by the hypothalamus. It is stored in the posterior pituitary and released when needed

as indicated by serum osmolality levels. A high serum osmolality indicates that the

serum is concentrated and that the amount of water is limited. When this occurs,

ADH is released. ADH increases the permeability of the distal renal tubules and collecting

ducts, resulting in water reabsorption. Conversely, a low serum osmolality

indicates there is a water excess and that the serum is dilute. In this situation, ADH

secretion is reduced, leading to increased excretion of water (diuresis).

Certain conditions can result in an abnormal secretion or lack of secretion of

ADH, or in a lack of renal response to ADH secretion. In diabetes insipidus, there

is either inadequate ADH secretion or the kidneys do not respond appropriately to

ADH. Causes of diabetes insipidus include head trauma, brain tumor or inflammation,

neurosurgical procedures, or primary renal diseases. In the syndrome of inappropriate

antidiuretic hormone secretion (SIADH), there is continuing release of

ADH in the presence of low plasma osmolality. SIADH may be caused by ectopic

ADH-producing tumors of the lung, thymus, pancreas, intestines, and urologic tract;

by some pulmonary conditions; or by extreme stress.

Normal Values

1–5 pg/mL (1–5 ng/L SI units)

Possible Meanings of Abnormal Values

Increased                                                                        Decreased

Acute porphyria                                                              Central (pituitary) diabetes insipidus

Addison’s disease                                                           Head trauma

Brain tumor                                                                    Hypervolemia

Bronchogenic cancer                                                      Hypothalamic tumor

Circulatory shock                                                           Metastatic disease

Ectopic ADH secretion                                                  Neurosurgical procedures

Hemorrhage                                                                    Sarcoidosis

Hepatitis                                                                         Syphilis

Hypothyroidism                                                             Viral infection

Hypovolemia

Nephrogenic diabetes insipidus

Pneumonia

Stress

Syndrome of inappropriate ADH secretion (SIADH)

Tuberculosis

Contributing Factors to Abnormal Values

• Test results can be altered by: physical and psychological stress, positive-pressure

  mechanical ventilation, use of glass tube for blood sample collection.

• Drugs that may increase ADH levels: acetaminophen, anesthetics, barbiturates, carbamazepine,

  chlorothiazide, chlorpropamide, cyclophosphamide, estrogens,

  lithium, morphine, nicotine, oxytocin, vincristine.

• Drugs that may decrease ADH levels: alcohol, phenytoin.

Interventions/Implications

Pretest

• Explain to the patient the purpose of the test and the need for a blood sample to be

drawn.

• Fasting for 10 to 12 hours is required before the test. Physical activity and stress should

be avoided during this time.

Procedure

• A 7-mL blood sample is drawn in a prechilled lavender top (EDTA) plastic collection

tube. The patient should be in a sitting position.

• Gloves are worn throughout the procedure.

Post test

• Apply pressure at venipuncture site. Apply dressing, periodically assessing for continued

 bleeding.

• Label the specimen and transport it immediately to the laboratory in an ice bath. The

  blood sample must be centrifuged within 10 minutes of collection.

• Report abnormal findings to the primary care provider.