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Primary hyperparathyroidism (PHPT)<\/strong> is a metabolic bone disease characterizedby hypercalcemia<\/a>, hypophosphatemia, and inappropriately elevated PTHdue to autonomous production of parathyroid hormone by a parathyroid adenoma, hyperplasia or rarely, carcinoma.<\/p>\n The parathyroid glands were first discovered by Richard Owen in 1852 when he performed an autopsy on the Great Indian Rhinoceros kept by the Zoological Society of London. Owen, a professor of comparative anatomy in London, described the\u00a0parathyroid gland<\/a>\u00a0as \u201ca small yellow body attached to the thyroid\u201d during an autopsy of the rhinoceros. However, the discovery of the\u00a0parathyroid glands<\/a>\u00a0has been credited to Ivar Sandstr\u00f6m<\/strong>, who published the discovery in 1880 in a paper titled \u201con a New Gland in Man and Several animals.\u201d Due to the late anatomical description of these glands, they have often been referred to as \u201cthe last anatomic discovery.\u201d<\/p>\n These have been categorized into phenotypes varying from classic features of severe hyperparathyroidism characterized by target organ injury (urolithiasis and osteoporosis), through to mild biochemical and radiographic features without clinical symptoms to a disease entity with only mild elevation in serum parathyroid hormone levels.<\/p>\n The clinical phenotypes of primary hyperparathyroidism (PHPT) over the past 50 years.<\/strong><\/p>\n Before 1970 :<\/strong> A disease of bones, stones, groans, and psychiatric moans and fatigue overtones. This is the classic symptom pentad of primary hyperparathyroidism which was seen in most patients prior to the universal assessment of serum calcium in patients seen in health care settings.<\/p>\n 1970-2000:<\/strong> A disease with primarily biochemical and densitometric signatures.<\/p>\n After 2000:<\/strong> A disease that may present at first with a more subtle biochemical signature \u2013 elevated parathyroid hormone (PTH) levels with normal serum calcium.<\/p>\n This disease entity was recognized at the time of the Third International Workshop. Subsequently, formal diagnostic criteria and management recommendations were made at the Fourth International Workshop. Nonetheless, there is still no evidence to guide physicians regarding management decisions<\/p>\n Diagnostic features of normocalcemic primary hyperparathyroidism<\/strong><\/p>\n *4-64% of patients with a diagnosis of normocalcemic PHPT were reclassified as having traditional hypercalcemic disease<\/strong> with measurement of ionized calcium based on a study by Nordensterom et al.<\/p>\n Secondary causes of hyperparathyroidism would need to be excluded before making a diagnosis of the normocalcemic variant of primary hyperparathyroidism.<\/p>\n A proposed mechanism for this condition is significant target tissue resistance to PTH action. Subsequently, there is steady rise in PTH which precedes the onset of overt hypercalcemia by an unspecified period. It can therefore be seen as a forme fruste<\/em> of classic PHPT.\u00a0<\/strong><\/p>\n In a small randomized controlled trial by Cesareo et al the authors treated patients with normocalcemic PHPT and low bone mineral density with either alendronate or cholecalciferol. They observed a statistically significant increase in bone density in patients with normocalcemic PHPT treated with alendronate (n=15) vs cholecalciferol alone (n=15)<\/p>\n In a small unblinded pilot study of 6 patients with normocalcemic PHPT using cinacalcet at a dose sufficient to decrease PTH levels, the authors reported a low number and diameter of kidney stones. The significance of this finding would need to be tested in future studies.<\/p>\n There is limited data to show normocalcemic patients after surgery have improvement in bone density, nephrolithiasis, cardiovascular parameters, and quality of life.<\/p>\n\n![\"Primary](\"https:\/\/myendoconsult.com\/learn\/wp-content\/uploads\/primary-hyperparth.webp\")
<\/p>\nPhenotypes of primary hyperparathyroidism<\/h2>\n
What is the normocalcemic variant of primary hyperparathyroidism<\/h2>\n
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Mechanism of normocalcemic primary hyperparathyroidism<\/h2>\n
Medical management of normocalcemic primary hyperparathyroidism<\/h2>\n
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Surgical management of normocalcemic primary hyperparathyroidism<\/h2>\n