Maintenance of Serum Calcium Level in Older People

Introduction

Calcium is an important nutrient required for normal growth and development. It is the most abundantly stored nutrient in the human body, as approximately 99 percent is stored in the bones and teeth, providing skeletal strength, and about one percent as extracellular serum calcium. The extracellular pool of calcium, around 1200 to 1400 mg (milligrams), with the hormones such as calcitonin, calcitriol, parathyroid hormone, and other substances, helps maintain the plasma calcium levels. Serum calcium levels do not fluctuate with the changes in the diet; however, a small drop below the normal level may trigger an immediate response. The body prevents hypocalcemia by transferring calcium from other sources and maintains serum calcium levels; thus, serum calcium is not an indicator of calcium stored in the body.

What Is the Role of Calcium in Human Health?

The metabolism of calcium also involves other nutrients, such as proteins, vitamin D, and phosphorus. The kidneys, intestines, and bones play an important role in calcium absorption. The equilibrium of calcium in the body is maintained by absorption in the intestines, movement in and out of the bones, and excretion of the calcium from the kidneys into the urine. When the serum calcium levels decrease, the parathyroid glands release the parathyroid hormone (PTH) into the blood, and the osteoclasts (bone-resorbing cells) release the calcium from the bone surfaces. It also prevents the excretion of calcium in the urine. A dietary intake of 1000 mg of calcium per day would make approximately 800 mg available for tissue nutrient requirements and 200 mg for maintaining serum calcium levels.

What Are the Functions of Calcium?

• Calcium is required for various functions in the body, such as skeletal mineralization, vascular contraction, vasodilation, nerve transmission, clotting mechanisms, hormonal secretions, intracellular signaling, and the proper functioning of the muscles. Any variation in the serum calcium levels may affect these functions.

• Maintenance of bone formation is a lifelong process, and adequate calcium intake is required to reduce the risk of fractures, osteoporosis, and other disorders. Adequate calcium consumption in the early years may provide more stable bone mass during aging. Approximately 40 percent of the calcium in the blood is bound to proteins, especially albumin, and acts as a source of calcium for the cells and helps maintain normal cellular function.

Who Is at Risk for Calcium Deficiency?

People at risk for dietary calcium deficiency include post-menopausal women, adolescents, the elderly, and individuals with lactose intolerance (allergy to milk and milk products). Elderly people are at increased risk due to dietary habits, underlying chronic diseases, hormonal changes, low calcium intake, reduced calcium absorption, and drug interactions, etc. Studies show that after the age of 50, bone density often decreases, which leads to an increased risk of fractures.

What Are the Signs and Symptoms Associated With Varying Calcium Levels?

A variation in serum calcium levels can cause the symptoms such as:

• Muscle cramps and spasms.

• Brittle nails.

• Dry and scaly skin.

• Irritability and confusion.

• Memory problems.

• Seizures.

• Tingling sensation in the lips, tongue, and limbs.

• Arrhythmia (abnormal heart rhythm).

• Pain in the bones and joints.

What Are the Causes for Varying Serum Calcium Levels in Elderly People?

Many factors are involved in maintaining the serum calcium levels in the body, and any variation in these can affect elderly individuals. Some of the causes include:

• Decreased levels of parathyroid hormone can result in a reduction of calcium in the body.

• A deficiency of vitamin D can affect the absorption of calcium.

• Patients with kidney disorders or kidney failure can have increased phosphorus levels and an imbalance in maintaining the serum calcium equilibrium.

• Certain medications, such as Rifampicin, corticosteroids, bisphosphonates, etc., can affect serum levels in the body.

• Most patients suffering from pancreatic disorders like acute pancreatitis have decreased calcium levels.

How Can Serum Calcium Levels Be Maintained in Older People?

The calcium balance is calculated based on the net difference between the total amount of calcium ingested and the total amount lost primarily through fecal excretion and a smaller amount through the other body tissues like the skin, nails, hair, and body secretions like sweat. This delicate calcium balance often stays on the positive side during the growth of the individual, stays at net zero on reaching full maturity, but reduces to negative during aging, similarly as all other tissues also decline.

Studies have suggested an average intake of 1100 to 1200 mg of calcium in adults as a threshold above which the intake of extra calcium would not improve the skeletal health of the individual. With advancing age, calcium and vitamin D absorption reduces and is also associated with a decline in renal function, affecting bone health.

• Hypoparathyroidism in the elderly is rarely seen and is mostly secondary to surgery involving the neck, characterized by predominant psychiatric and neuromuscular symptoms due to hypocalcemia. The treatment involves the administration of calcium and vitamin D.

• Hyperparathyroidism in the elderly is more frequently seen than hypoparathyroidism, with clinical presentations mimicking the normal signs of aging.

• Mild hypercalcemia is often incidentally detected and needs radiological tests and serum levels of vitamin D to diagnose certainty. In such cases, surgical management of parathyroidectomy (removal of the parathyroid gland) can be considered to prevent fractures in the elderly after a risk-benefit analysis.

It is essential to remember that those with chronic hypocalcemia have very subtle symptoms or may even be asymptomatic with mild reductions in serum calcium. Severe cases need hospitalization and administration of calcium intravenously, along with monitoring of the vitals. In mild to moderate cases, administration of calcium and vitamin D can be advised on an outpatient basis.

The choice of administration of vitamin D depends on the cause of hypocalcemia. Calciferol, either vitamin D2 or D3, is often recommended. It needs the conversion to the active metabolite of vitamin D by the parathyroid hormone. It has a long half-life of 10 to 14 days with a slow onset in its action.

In hypoparathyroidism patients, it is advisable to start with calcitriol, an active analog of vitamin D, at a dose of 0.25 to 0.5 micrograms with an additional dose on a gradual upward titration till the normal levels of serum calcium are achieved. Calcitriol has a very rapid onset and requires careful monitoring of serum calcium. It has a very short half-life and makes the patient vulnerable to symptoms of hypocalcemia. It is essential to frequently monitor 24-hour calcium, serum phosphate, and creatinine in patients with hypoparathyroidism. Thiazide diuretics with a low salt diet are also recommended to reduce the risk of kidney disorders.

Conclusion

Calcium is an important nutrient required for normal growth and development. The metabolism of calcium also involves other nutrients, such as proteins, vitamin D, and phosphorus. The kidneys, intestines, and bones play an important role in calcium absorption. With advancing age, calcium and vitamin D absorption reduces and is also associated with a decline in renal function, affecting bone health. Therefore, maintaining serum calcium levels by following a healthy diet or calcium supplements is essential to prevent complications.