Endocrine Abstracts

Calcium (Ca) is critical for a multitude of biological processes in the human body. Ca concentration is therefore tightly controlled in all age groups between 2.2-2.7 mmol/l. When Ca intake is low, extracellular fluid Ca can potentially decrease. The parathyroid cell is exquisitely sensitive to minor alterations in Ca level and a rise in PTH normalises the reduced serum Ca concentration because of its action on (1) the intestine, by increasing Ca absorption, indirectly by its effects on calcitriol (1,25(OH)2D) production, (2) the bone, by increasing Ca efflux from the bone and (3) the kidneys, by increasing Ca reabsorption and excreting inorganic phosphorus. Hypocalcemia can occur at any age; it may arise because of inadequate calcium supply (reduced dietary intake or vitamin D deficiency or defects in its metabolism), following an acute increase in plasma phosphate concentration, impaired parathyroid hormone (PTH) secretion and end-organ resistance to PTH (e.g., pseudohypoparathyroidism). Hypomagnesemia impairs PTH secretion and leads to resistance to the action of PTH on the bone and kidney. Hypercalcemia develops when the rate of calcium entry into the extracellular fluid exceeds the kidneys' capacity for its excretion. It occurs when there is increased absorption of calcium from the gastrointestinal tract, increased release of calcium from the skeleton or decreased excretion of calcium from the kidneys. Symptoms of hypercalcemia in infants are often non-specific and include feeding difficulties, vomiting, constipation, failure to thrive, irritability and hypotonia. Older children may present with anorexia, non-specific abdominal pain, muscle weakness, polydipsia and polyuria, dehydration, and neuropsychiatric symptoms. Chronic hypercalcemia and accompanying hypercalciuria may predispose to nephrocalcinosis and, if left untreated, renal impairment. In this presentation, I will discuss my approach to the investigation and management of hypo and hypercalcaemia using some of the cases I have managed in my practice.