Hyperparathyroidism overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief:
Overview
Hyperparathyroidism is overactivity of the parathyroid glands resulting in excess production of parathyroid hormone (PTH). The parathyroid hormone monitors calcium and phosphorus levels and helps to maintain these levels. Overactivity of one or more of the parathyroid glands causes high calcium levels (hypercalcemia) and low levels of phosphorus in the blood. Hyperparathyroidism was first described and treated in the 1930s by Fuller Albright of Massachusetts General Hospital, working at the Mallinckrodt General Clinical Research Center. The oldest known case was found in a cadaver from a Early Neolithic cemetery in southwest Germany.[1]
Historical Perspective
In 1880, Ivar Sandström, a Swedish anatomist, described parathyroids in human following 50 autopsies. In 1924, James Bertram Collip, a Canadian biochemist, discovered and extracted parathormone and treated tetany with the help of parathyroid extract along with Douglous B Leitch. In 1925, Felix Mandl, a viennese surgeon performed first parathyroidectomy to treat a patient suffering from suffering from osteitis fibrosa cystica. In 1959, Howard Rasmussen and Lyman C. Craig at the Rockefeller Institute for Medical Research purified parathyroid hormone. They also isolated the active polypeptide (parathormone B) from bovine parathyroid gland and gave its tentative formula in 1961.
Classification
Hyperparathyroidism can be classified into primary, secondary and tertiary. Primary hyperparathyroidism results from a hyperfunction of the parathyroid glands themselves. There is oversecretion of PTH due to adenoma, hyperplasia or, rarely, carcinoma of the parathyroid glands. Secondary hyperparathyroidism is due to increase in secretion of parathyroid hormone from a secondary process. Tertiary hyperparathyroidism is a state of excessive secretion of parathyroid hormone (PTH) after a long period of secondary hyperparathyroidism and resulting in hypercalcemia.
Pathophysiology
Hyperparathyroidism is an increase in serum parathyroid hormone. Normally, parathyroid hormone increases serum calcium and magnesium concentration, and decreases serum phosphate concentration. Secretion of parathyroid hormone from parathyroid gland is stimulated by low serum calcium. Parathyroid glands have calcium-sensing receptors responsible for sensing extracellular ionized calcium. Calcium and magnesium provides a negative feedback for secretion of parathyroid hormone. Primary hyperparathyroidism is due to increase in secretion of parathyroid hormone from a primary process in parathyroid gland.Majority of times, increase in secretion of parathyroid hormone is the result of parathyroid adenoma (85%). Calcium-sensing receptor expression in reduced in parathyroid adenoma resulting in an increase in calcium sensing set point. In minority of cases, development of primary hyperparathyroidism is the result of multiple genetic mutations. Genes involved in the pathogenesis of primary hyperparathyroidism include calcium-sensing receptor gene, HRPT2 gene (CDC73 gene), Cyclin D1 gene (CCND1)/PRAD1 gene, MEN1 gene, and RET gene. Secondary hyperparathyroidism is due to increase in secretion of parathyroid hormone from a secondary process, most commonly due chronic renal failure. Fibroblast growth factor 23 (FGF-23) concentration increases in chronic renal failure which plays a central role in regulation of phosphate vitamin D homeostasis and pathogenesis of secondary hyperparathyroidism. Majority of times, tertiary hyperparathyroidism occurs in patients after renal transplantation.Patients with secondary hyperparathyroidism continues to have elevated parathyroid hormone even after renal transplantation. Classically, there is hyperplasia of all four of parathyroid gland. On gross pathology, parathyroid adenoma is a soft, tan nodule which is well-circumscribed by a delicate capsule. Typically, cut surface of parathyroid adenoma is smooth, soft, and reddish brown in color. It should be differentiated from normal parathyroid gland tissue which is yellow-brown color. Parathyroid hyperplasia usually involves multiple glands. Bones and kidney are also commonly involved in hyperparathyroidism. Hypercalcemia due to hyperparathyroidism may cause metastatic calcification in many organs including lungs, heart, blood vessels, stomach. Chief cells are predominant in parathyroid adenoma on microcopy. Adenoma is seperated from a rim of non-neoplastic tissue on the edge by a fibrous capsule. Endocrine atypia (cells with bizarre and pleomorphic nuclei) is often seen in parathyroid adenoma. It should not be mistaken as a sign of malignancy. Majority of times, hyperplasia of chief cells is observed in parathyroid hyperplasia. It may be diffuse or multinodular. Cytologic details are unreliable for diagnosis of parathyroid carcinoma.
Causes
Hyperparathyroidism is caused by an increase in concentration of parathyroid hormone in serum. There are three type of hyperparathyroidism including primary, secondary and tertiary hyperparathyroidism. There are an array of different causes for all types of hyperparathyroidism. Most common cause of primary hyperparathyroidism is parathyroid adenoma (85%) folllowed by parathyroid hyperplasia (15%), and parathyroid carcinoma (5%). Most common cause of secondary hyperparathyroidism is chronic renal failure and vitamin D deficiency. Most common cause of tertiary hyperparathyroidism is chronic renal failure.
Differentiating ((Page name)) from Other Diseases
There are three types of hyperparathyroidism (primary, secondary, and tertiary) and should be differentiated between each other. Hyperparathyroidism should be differentiated from other causes of hypercalcemia. Causes of hypercalcemia other than hyperparathyroidism include familial hypocalciuric hypercalcemia, hypercalcemia related to malignancy, medication-induced hypercalcemia, hypercalcemia due to nutritional disorders, and hypercalcemia related to granulomatous diseases.
Epidemiology and Demographics
Primary hyperparathyroidism is the 3rd most common endocrine disorder. Highest incidence of primary hyperparathyroidism is in post-menopausal women.The incidence of primary hyperparathyroidism is approximately 0.4 to 21.6 per 100,000 person years. The prevalence of primary hyperparathyroidism is approximately .01 to .07 per 100,000 individuals. The incidence of primary hyperparathyroidism increases with age. Primary hyperparathyroidism usually affects individuals of African-American race. Women are more commonly affected by primary hyperparathyroidism than men. The women to men ratio is approximately 3 to 1. Difference in gender specific incidence of primary hyperparathyroidism becomes more pronounced with advancing age. There is insufficient data on epidemiology and demographics of secondary and tertiary hyperparathyroidism.
Risk Factors
Common risk factors in the development of primary hyperparathyroidism include postmenopausal women, age group 50-60 year, family history of hyperparathyroidism, and history of familial syndromes. Common risk factors in the development of secondary hyperparathyroidism in chronic renal failure include high serum phosphorus expression levels, low serum creatinine expression levels, low serum calcium expression levels, female gender, and hypertension. Common risk factors in the development of tertiary hyperparathyroidism post renal transplantation include elderly individuals and longer duration of dialysis.
Screening
There is insufficient evidence to recommend routine screening for hyperparathyroidism.
Natural History, Complications, and Prognosis
Primary hyperparathyroidism usually develops in the fifth decade of life, in post-menopausal women and starts as asymptomatic hypercalcemia in presence of increased parathyroid hormone. If left untreated, some of patients with primary hyperparathyroidism may commonly develop marked hypercalcemia, marked hypercalciuria, cortical bone demineralization and nephrolithiasis.
Secondary hyperparathyroidism arise in the early course of chronic renal failure. As renal failure progress, secondary hyperparathyroidism becomes more notable. If left untreated, secondary hyperparathyroidism carries an increased risk of vascular calcification with increasing age and duration of dialysis in patients.
Tertiary hyperparathyroidism usually develops in post renal transplant patients. If left untreated, tertiary hyperparathyroidism in post renal transplant patients may carry the risk of amyloid deposition, calciphylaxis, destructive or erosive spondyloarthropathy, osteonecrosis, and musculoskeletal infections.
Hyperparathyroidism leads to a variety of complications in various organ systems depending on the type of hyperparathyroidism.
Prognosis is all types hyperparathyroidism is generally good after proper treatment.
Diagnosis
History and Symptoms
The majority of patients with primary hyperparathyroidism are asymptomatic. Asymptomatic primary hyperparathyroidism patient is expected to develop signs and symptoms, but most of the patients does not becomes symptomatic with time. The hallmark of primary hyperparathyroidism is asymptomatic hypercalcemia. The classic signs and symptoms of primary hyperparathyroidism are present in a few individuals and are summarized by the mnemonic painful bones, kidney stones, abdominal groans, psychic moans, and fatigue overtones. The majority of patients with secondary hyperparathyroidism have a history of either chronic renal failure or long term vitamin D deficiency. The majority of patients with tertiary hyperparathyroidism have a history of renal transplantation.
Physical Examination
Physical examination of patients with hyperparathyroidism is usually unremarkable. Patients may have physical findings due to severe hypercalcemia and other complications of hyperparathyroidism.
Laboratory Findings
Electrocardiogram
X-ray
CT scan
MRI
Ultrasound
Other Imaging Findings
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Primary Prevention
Secondary Prevention
References
- ↑ Zink AR, Panzer S, Fesq-Martin M, Burger-Heinrich E, Wahl J, Nerlich AG (2005). "Evidence for a 7000-year-old case of primary hyperparathyroidism". JAMA. 293 (1): 40–2. doi:10.1001/jama.293.1.40-c. PMID 15632333.