SERUM CALCIUM and medicinal hypocalcemia

SERUM CALCIUM makes it possible to evaluate the disorder of calcium metabolism. Besides, an increase of concentration can establish at malignant tumours. Also, osteolysis resulting from the release of peptides with action similar to the effect of the thyrotropic hormone. Primary hyperfunction of parathyroid glands, overdosage of D vitamin, myeloma, chronic enteritis (IVth stage).

Medicinal hypocalcemia

Decrease of serum calcium concentration is possible at

• hypo-activity of parathyroid glands (after surgical interventions, aplasia of parathyroid glands, auto immunisation).
• Secondary hyper-function of parathyroid glands (insufficiency of D vitamin or resistance to it, chronic renal failure).
• And sequestration of calcium ions (acute alkalosis, a rise of phosphates, abundant transfusion of citrated blood).
• Osteomalacia of hypoalbuminemia, medicinal hypocalcemia (while receiving calcitonin, ethylene-diamine-tetraacetic acid, citrus, neomycin, fenobarbitalum).

Characteristics of hypocalcemia

Below-normal serum calcium concentrations of 8.5-10.5 mg / dl (2.1-2.5 mmol / l characterise hypocalcemia. The introduction into clinical practice of routine biochemical studies has contributed to the improvement of the diagnosis of disorders of calcium metabolism, especially asymptomatic hypercalcemia. Despite the fact that, on the whole, hypocalcemia is less common in ambulatory patients, it can occur more often in patients with malignant neoplasms and kidney diseases than hypercalcemia.

Typically, the serum concentration of calcium is maintained within 2.2-2.6 mmol / l. However, ionized or protein-unbound calcium is slightly less than half of the total calcium. Ionized calcium, which is a physiologically active fraction, takes part in many diverse metabolic processes. Significant changes in serum protein concentration, essentially albumin disrupt the level of total serum calcium. A simple way to correct the results of determining calcium in the blood is to increase the resulting calcium concentration by 0.25 mmol / L while decreasing the serum albumin concentration for every 10 g / L relative to the norm. Profound disturbances of calcium protein binding occur under the influence of changes in blood pH: an increase in pH leads to an increase in binding and, consequently, a decrease in the content of ionized calcium. This law explains the occurrence of symptoms of hypocalcemia in hyperventilating respiratory alkalosis.