Top 10 laboratory tests: blood will tell - includes related information - part 1

FDA Consumer, July-August, 1989 by Dixie Farley

Significance of results: Increased sodium concentration in plasma is seen mostly in the elderly and in very ill patients. It suggests water loss in excess of sodium loss (as in severe vomiting or diarrhea or the excessive urination of diabetes insipidus) or sodium increase in excess of water (as in people who don't drink enough water and are dehydrated). On the other hand, low sodium concentration can occur if sodium loss exceeds water loss during a severe water-loss situation (as in prolonged diarrhea) or if sodium is inadequately conserved (as in chronic kidney disease). Low sodium concentration also can indicate insufficient aldosterone. An abnormally low sodium level generally causes symptoms such as fatigue, weakness, apprehension, and convulsions. Dry, sticky mucous membranes, flushed skin, elevated body temperature, lack of tears, and thirst are among the symptoms of sodium excess.

Calcium, a Possible Clue to Many Problems

Measurement: The level of calcium in serum.

Normal range: 9.0 to 10.5 mg/dL.

Use: To gather evidence about bone disease, certain cancers, kidney failure, or overactivity of the parathyroid gland.

Comments: Calcium is absorbed from the diet and excreted in both urine and stool. Most of the body's calcium is combined with phosphate and carbonate and serves to strengthen the bones. Only about 10 percent is in the form of electrically charged particles circulating in the blood. Nevertheless, calcium cations are essential for nerve impulse transmission, heart activity, and blood clotting. When serum calcium drops below normal, the parathyroid releases a hormone that triggers a series of events: The gastrointestinal tract absorbs more calcium, the kidneys break down and assimilate calcium, and the bones release calcium into the blood. When serum calcium levels return to normal, this hormone secretion decreases.

Significance of results: Too much dietary calcium, too much vitamin D, prolonged immobilization (as in bed rest), leukemia, bone tumors, parathyroid overactivity, kidney disease, some cancers--all can contribute to high blood calcium. Symptoms include constipation, decreased appetite, nausea, weight loss, kidney stones, and deep body pain. Daily exercise such as walking (or isotonic exercises by people confined to bed) can help maintain normal calcium levels. Calcium deficiency can occur when the small intestine doesn't properly absorb the mineral, as happens with inflammation of the pancreas and Crohn's disease. Some calcium is bound to protein, so too much protein intake causes the bound calcium to leave the bones and be excreted, leading to the bone-thinning disease osteoporosis. Removal of parathyroid tissue (which can happen during a thyroid operation) causes calcium loss. A person in need of calcium may have tingling in the finger tips, muscle cramps, numbness, and overactive reflexes. Foods rich in calcium include milk and other dairy products, broccoli, collards, tofu, and canned sardines or salmon with bones.