Certain urological conditions may have a direct impact on skeletal activity and calcium metabolism. Most of the body calcium and phosphate is tightly packed in bones and serum calcium levels and is kept constant by a complex interaction between vitamin D, parathyroid hormone (PTH), and calcitonin. Alkaline phosphatase (ALP) levels increase with abnormal osteoblastic activity in bone. Some common examples of interactions between bone disease and urological conditions include—

• Renal calculi and hypercalcemia-hyperparathyroidism, meta-static bone disease

• Androgen deprivation for prostate cancer and osteoporosis

• Effects of chronic renal failure (CRF) on bone mineralisation

Normal reference range is presented in Table 2.6. Hypercalcemia

The renal effects of hypercalcemia include an increased glo-merular filtration of calcium (hypercalciuria) as well as increased urinary phosphate excretion. The urological effects of these include—

• Renal stone formation

• Nocturia/polyuria—due to decreased concentrating effects of the renal tubule, secondary to hypercalciuria

TABLE 2.6. Normal reference range for markers of bone activity

Serum Levels Normal Range

Calcium 2.2-2.6 mmol/L

Phosphate 0.8-1.45 mmol/L

PTH 10-65 ng/L

ALP 90-300 IU/L

Urological patients with hypercalcemia must be investigated for possible causes, which include—

• Excess PTH—primary (pituitary adenoma) or tertiary (secondary to renal failure)

• Malignant disease (most common cause of hypercalcemia in the in-patient setting)—bone metastases from prostate, kidney, etc. Hypercalcemia may be due to direct destruction of bone or production of a bone-resorption substance called PTH related polypeptide

• Excess Vit D—iatrogenic or self-administered; sarcoidosis

• Others—"milk alkali" syndrome, immobility Osteoporosis

• Castration, either medical (LHRH analogue) or surgical can cause a reduction of up to 17% in the bone mineral density in patients over 3 years

• Maximum loss occurs within the first year of treatment

• May lead to an increased incidence of osteoporosis and subsequent osteoporotic fractures

• Recommended that all patients commencing on androgen deprivation therapy should undergo surveillance checks on bone mineral density starting at 1 year onwards

Osteoporosis is not a disease of calcium metabolism and therefore serum calcium, phosphate, and ALP are often within normal limits. Ideally patients should undergo—

• Bone mass evaluation (DXA—double x-ray absorptiometry) scan

• Measurement of urinary NTx (type 1 collagen N-telopeptides), a bone marker for resorption suggesting increased bone turnover

TABLE 2.7. Trends in serum bone markers in pathological conditions




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