Hyperparathyroidism

The most common cause of hyperparathyroidism is Parathyroid adenoma. Another cause is hyperplasia of the parathyroid glands.

Parathyroid hormone (PTH) increases serum calcium by

·         Enhancing distal tubular calcium reabsorption

·         Rapidly mobilizing calcium and phosphate from bone (bone resorption)

·         Increasing intestinal absorption of calcium by stimulating conversion of vitamin D to its most active form, calcitriol

Hyperparathyroidism is characterized as:

·         Primary: Excessive secretion of PTH due to a disorder of the parathyroid glands

·         Secondary: Hypocalcemia due to non-parathyroid disorders leads to chronic PTH hypersecretion

·         Tertiary: Autonomous secretion of PTH unrelated to serum calcium concentration in patients with long-standing secondary hyperparathyroidism

Primary hyperparathyroidism: excessive secretion of PTH by one or more parathyroid glands. Incidence increases with age and is higher in postmenopausal women. Primary hyperparathyroidism causes hypercalcemia, hypophosphatemia, and excessive bone resorption (leading to osteoporosis).

Secondary hyperparathyroidism occurs most commonly in advanced chronic kidney disease when decreased formation of active vitamin D in the kidneys and other factors lead to hypocalcemia and chronic stimulation of PTH secretion. Hyperphosphatemia that develops in response to chronic kidney disease also contributes. Other less common causes of secondary hyperparathyroidism include

·         Decreased calcium intake

·         Poor calcium absorption in the intestine due to vitamin D deficiency

·         Excessive renal calcium loss due to loop diuretic use

·         Inhibition of bone resorption due to bisphosphonate use

Tertiary hyperparathyroidism results when PTH secretion becomes autonomous of serum calcium concentration and generally occurs in patients with long-standing secondary hyperparathyroidism, as in patients with ESRD of several years’ duration.

Indications of surgery:

·         Serum calcium 1 mg/dL greater than the upper limits of normal

·         Calciuria > 400 mg/day

·         Creatinine clearance < 60 mL/minute

·         Peak bone density at the hip, lumbar spine, or radius 2.5 SD below controls (T score = −2.5)

·         Age < 50 years

·         The possibility of poor adherence with follow-up

Secondary hyperparathyroidism in patients with renal failure can result in a number of symptoms, including

·         Osteitis fibrosa cystica with arthritis, bone pain, and pathologic fractures

·         Spontaneous tendon rupture

·         Proximal muscle weakness

·         Extra-skeletal calcifications, including soft tissue and vascular calcification

·         Pruritis