Specimen Information

Type

Gold, SST

Volume

1.0 ml

Transport Info

Refrigerated

Fasting Required?

False

Clinical Significance

Used in the diagnosis and treatment of aldosteronism (excessive secretion of the hormone aldosterone), diabetes insipidus (chronic excretion of large amounts of dilute urine, accompanied by extreme thirst), adrenal hypertension, Addison's disease (caused by destruction of the adrenal glands), dehydration, inappropriate antidiuretic hormone secretion, or other disease involving electrolyte imbalance.

Sodium (Na+) is the major positive ion of the extracellular (outside of the cell) fluids. The concentration of sodium inside cells is only about 5 mEq/L compared to 140 outside. Sodium is the major determinant of extracellular osmolality. The sodium content of the blood is a result of a balance between dietary intake and renal excretion (only a small percent is lost through the stool or sweat).Many factors affect sodium levels, including the steroid hormone aldosterone (for more information see the aldosterone test) which decreases loss of sodium in the urine. Atrial natriuretic protein (ANP) is a hormone secreted from the heart that increases sodium loss from the body. Water and sodium are interrelated in that, for example, retention of increased sodium is followed by retention of fluid and vice versa. However, the body is able to regulate sodium and water separately if necessary, controlling sodium by means of aldosterone and ANP and water by ADH (antidiuretic hormone). Increased Na+ levels (hypernatremia) may indicate: - Cushing’s syndrome (rare) - Dehydration - Diabetes insipidus - Extensive thermal burns - Hyperaldosteronism (very rare) - Osmotic diuresis. Decreased Na+ levels (hyponatremia) may indicate: - Addison’s disease (rare) - Ascites (leakage of fluid into the peritoneum and commonly seen in cirrhosis of the liver) - Congestive heart failure - Diarrhea - Excessive sweating - Intraluminal bowel loss (ileus or mechanical obstruction) - Ketoacidosis - Kidney disease - Osmotic dilution - Peripheral edema - Pleural effusion - Syndrome of inappropriate antidiuretic hormone secretion - Vomiting or nasogastric aspiration - Use of diuretics. Additional conditions under which Na+ testing may be performed: - Acute adrenal crisis - Diabetic hyperglycemic hyperosmolar coma - Drug-induced hypothyroidism - Hepatorenal syndrome - Hypopituitarism - Hypothyroidism - Hypothyroidism; primary - Hypothyroidism; secondary.