Hypoparathyroidism

Under physiologic circumstances, calcium concentration in the extracellular fluid is maintained within a very narrow range. Normal calcium homeostasis depends on a complex set of hormonal regulatory mechanisms that include the effects of parathyroid hormone (PTH), vitamin D metabolites, and calcitonin on calcium transport in bone, kidneys, and the gastrointestinal tract. Parathyroid hormone deficiency results in hypocalcemia, hyperphosphatemia, and increased neuromuscular irritability with myalgias, muscle spasms, and in extreme cases, tetany.