Calcium (blood)

The majority of body calcium is bone-associated and circulating levels reflect bone turnover and disease. Circulating calcium is under the control of parathyroid hormone. The parathyroid gland mediates increased serum calcium as a function of PTH production. Primary hyperparathyroidism reflects adenoma/carcinoma or hyperplastic syndromes, leading to excess serum calcium as a function of bone mineralisation and increased renal reabsorption/intestinal uptake. Secondary forms typically reflect renal failure.

Increased calcium and reduced phosphate typically reflects primary hyperparathyroidism, while raised phosphate is seen in secondary forms Raised calcium is seen in osteomalacia, osteoporosis, Paget’s disease and osteolytic lesions secondary to bone metastasis Reduced serum calcium is associated with hypomagnesaemia, rickets and vitamin D deficiency Diagnosis and assessment of recurrent urolithiasis patients in addition to monitoring the effectiveness of thiazide therapy to lessen calciuria in known stone formers