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Tertiary Hyperparathyroidism | |
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Thyroid and parathyroid | |
Specialty | Endocrinology |
Symptoms | None, kidney stones, weakness, depression, bone pains, confusion, increased urination |
Complications | Osteoporosis |
Usual onset | 50 to 60 |
Types | Primary, secondary, tertiary |
Causes | Tertiary: parathyroid adenoma, multiple benign tumors, parathyroid cancer, parathyroid hyperplasia, growth of parathyroid tissue, secondary hyperparathyroidism |
Diagnostic method | High blood calcium and high PTH levels |
Treatment | Surgery, intravenous normal saline |
Frequency | ~2 per 1,000 |
Tertiary hyperparathyroidism is a condition involving the overproduction of the hormone, parathyroid hormone, produced by the parathyroid glands. [1] The parathyroid glands are involved in monitoring and regulating blood calcium levels and respond by either producing or ceasing to produce parathyroid hormone.
Anatomically, these glands are located in the neck, para-lateral to the thyroid gland, which does not have any influence in the production of parathyroid hormone. Parathyroid hormone is released by the parathyroid glands in response to low blood calcium circulation. Persistent low levels of circulating calcium are thought to be the catalyst in the progressive development of adenoma, in the parathyroid glands resulting in primary hyperparathyroidism. While primary hyperparathyroidism is the most common form of this condition, [2] [3] [4] secondary and tertiary are thought to result due to chronic kidney disease (CKD). [2] Estimates of CKD prevalence in the global community range from 11 to 13% which translate to a large portion of the global population at risk of developing tertiary hyperparathyroidism. [5]
Tertiary hyperparathyroidism was first described in the late 1960s and had been misdiagnosed as primary prior to this. [6] Unlike primary hyperparathyroidism, the tertiary form presents as a progressive stage of resolved secondary hyperparathyroidism with biochemical hallmarks that include elevated calcium ion levels in the blood, hypercalcemia, along with autonomous production of parathyroid hormone and adenoma in all four parathyroid glands. [1] Upon diagnosis treatment of tertiary hyperparathyroidism usually leads to a surgical intervention. [7]
Symptoms in tertiary hyperparathyroidism are generally those seen in relation to elevated blood calcium levels. [8] [1] Tertiary hyperparathyroidism shares many symptomatic features with that of primary hyperparathyroidism, as the two are defined by hypercalcemia. These symptoms can vary greatly from asymptomatic to conditions leading to decreased quality of life. [1] [4]
Non-specific symptoms include feeling tired and thirsty; mood changes, including feeling low or depressed, weak and irritable; itching; headache; joint pain; forgetfulness; and abdominal pain. [8] [4] [9] [1] More specific symptoms related to elevated blood calcium and phosphate levels include bone pain or osteodynia and tenderness which are common and related to proximal muscle tenderness. Other signs can include pancreatitis, kidney stones, corneal calcifications, thinning of long bones, and hypodermic calcifications which may be palpable in some patients. [2] [4] [1]
Calciphylaxis, though uncommon, can develop in patients with tertiary hyperparathyroidism. The product of elevated calcium and phosphate, forming crystal structures, that are then deposited in blood vessels. These crystals cause an inflammatory response and can lead to the occlusion of smaller vessels. Further complications like secondary infections and necrosis can develop from this and can be fatal for some, making the monitoring of blood calcium and phosphate levels necessary. [8] [1]
Conditions due to bone loss such as osteopenia and osteoporosis are common in tertiary hyperparathyroidism along with pathologic fractures. Pseudoclubbing of the digits can also be indicative of a severe tertiary hyperparathyroidism due to excess resorption at the distal phalanges. [8] [1]
Diagnosis includes both clinical and laboratory investigations. Radiological investigations include looking for signs of bone loss in both the hands and pelvis which is characteristic of tertiary hyperparathyroidism. [8] Other clinical examination can include grading of muscle weakness, which is done by asking the patient to stand from a seated position with their hands folded across their chest. [4] [8] Laboratory investigations include evaluating blood calcium and alkaline phosphatase, which are always increased in tertiary hyperparathyroidism. Other common results from laboratory investigations would include decreased vitamin D levels, elevated blood parathyroid hormone and hyperphosphatemia. [9] [8] [1] [4]
Hyperparathyroidism , in general, is caused by either tumorous growth in one or more parathyroid glands or a prolonged decrease in blood calcium levels or hypocalcaemia which in turn stimulates the production of parathyroid hormone release from the parathyroid gland. [10] [11] The parathyroid gland is located beside the thyroid gland in the neck, below and in front of the larynx and above the trachea. It is composed of four glands in total that monitor blood calcium levels via the calcium sensing receptors, a g-coupled protein receptor. [12] The parathyroid glands main role is calcium homeostasis. [13] [12] Histologically, these glands are composed of chief cells and oxyphil cells with the chief cell primarily responsible for the storing and release of parathyroid hormone. These cells are arranged in a pseudo-follicular pattern similar to the thyroid follicles. Keratin staining is used to image the parathyroid hormone granules. [9] [14]
Parathyroid hormone is responsible for the induction of increased calcium absorption in the gastrointestinal tract or gut and in the kidney. It also induces calcium and phosphate resorption from the bone by osteoclasts. [15] [11] Parathyroid hormone also plays a role in activating vitamin D from its pro form to its active form. [15] Vitamin D is also responsible for increased blood calcium levels and works in conjunction with parathyroid hormone. Vitamin D is also partly responsible for the inhibition of parathyroid hormone release by binding Vitamin D receptors at the parathyroid gland. [11]
Tertiary hyperparathyroidism is defined by autonomous release of parathyroid hormone while in a hypercalcaemic state. Unlike primary hyperparathyroidism, hypercalcemia in the tertiary form is thought to be the result of resolution of secondary hyperparathyroidism rather than adenoma formation alone. [4] [11] [10]
Many of the mechanisms that drive the formation of tertiary hyperparathyroidism are due to outcomes of secondary hyperparathyroidism and so the tertiary from is said to be a continued progressive hyperparathyroidism. [10] [11] Secondary hyperparathyroidism occurs mainly in those who have chronic kidney disease or vitamin D deficiencies both of which lead to malabsorption of calcium and phosphate leading to decreased blood calcium levels inducing a hyperparathyroidism. Hyperphosphatemia in secondary hyperparathyroidism, due to increased parathyroid hormone, is thought to act directly on parathyroid glands and induce a hyperplasia or increased growth of the chief cells in particular. [11] At the same time the hyperplasic parathyroid glands have reduced fibroblast-growth-factor-23 (FGF-23) and vitamin D receptor expression. FGF-23 is partly responsible for phosphate homeostasis and provides negative feedback to the parathyroid gland as does vitamin D. [16] [17] [11]
During prolonged secondary hyperparathyroidism increased blood phosphate levels drive hyperplasia of the parathyroid gland and this acts to reset calcium sensitivity at the calcium sensing receptors leading to tertiary hyperparathyroidism after resolution of the secondary form with the continued release of parathyroid hormone in the presence of hypercalcemia. [11]
An elevated risk of developing tertiary hyperparathyroidism exists when late stage kidney disease is not corrected timely. [7] [4] This is due to a hyperphosphatemia acting directly on the parathyroid glands. Genetically, those who have an X-linked dominant disorder that disrupts phosphate transport at the renal tubules (X-Linked hypophosphatemic rickets) and are receiving oral phosphate treatment have shown to be at high risk of developing tertiary hyperparathyroidism in the absence of secondary hyperparathyroidism. [18] Recurring tertiary hyperparathyroidism is generally seen to be caused by incomplete parathyroidectomy without renal transplant and the risk is increased when the parathyroid tissue left after surgery is that of a nodular type. [7]
Other risk factors of tertiary hyperparathyroidism include an elevated risk of developing acute pancreatitis, mainly due to the hypercalcemia associated with the hyperparathyroidism. [19] Other studies have shown a significant increase in the risk of developing malignancies of the urinary tract and renal system with women being more at risk. [20] Though there is some conjecture as to the correlation between hyperparathyroidism and thyroid carcinoma development, there is however a correlation between the two, which is thought to be due to prolonged irradiation of the neck and head for parathyroid adenomas and increased parathyroid hormone. [21]
Other studies have found some correlation in the development of renal disease following parathyroidectomy. However, the mechanism for this effect remains unknown. [22]
Tertiary Hyperparathyroidism is almost always related to end stage kidney disease and a secondary hyperparathyroidism. [23] [4] [8] Physiological changes due to the kidney damage adversely affect feedback loops that control secretion of parathyroid hormone. Renal management of phosphate is impaired in secondary hyperparathyroidism which results in hyperphosphatemia. [4] [6]
Primary hyperplasia of the parathyroid gland, results from both hypocalcaemia and increased phosphate levels by decreasing expression of calcium sensing receptors and vitamin D receptors at the parathyroid gland. [8] [4] These decreases in receptor expression lead to hyperfunctioning of the parathyroid. Hyperfunction of the parathyroid gland is thought to exacerbate primary hyperplasia which evolves further to a secondary more aggressive hyperplasia. Histologically, these hyperplasic glands can be either diffuse or nodular. [24] Primary hyperplasia, usually resulting in diffuse polyclonal growth is manly related to reversible secondary hyperparathyroidism. Secondary hyperplasia of the parathyroid gland is more often a nodular, monoclonal growth that sustains secondary hyperparathyroidism and is the catalyst in the progression to tertiary hyperparathyroidism. Nodular hyperplastic glands in tertiary hyperparathyroidism are distinctly larger in both absolute size and weight up to 20-40-fold increases have been reported. [25] [26] [24]
Parathyroid glands are normally composed of chief cells, adipocytes and scattered oxyphil cells. [27] [14] Chief cells are thought to be responsible for the production, storage and secretion of parathyroid hormone. These cells appear light and dark with a prominent Golgi body and endoplasmic reticulum. In electron micrographs, secretory vesicles can be seen in and around the Golgi and at the cell membrane. These cells also contain prominent cytoplasmic adipose. [27] [14] Upon onset of hyperplasia these cells are described as having a nodular pattern with enlargement of protein synthesis machinery such as the endoplasmic reticulum and Golgi. Increased secretory vesicles are seen and decreased intercellular fat is characteristic. [27] [24] Oxyphil cells also appear hyperplasic however, these cells are much less prominent.[ citation needed ]
Biochemically, there are changes in function between normal and nodular hyperplastic parathyroid glands. These changes involve proto-oncogene expression and activation of proliferative pathways while inactivating apoptotic pathways. [28] In nodular parathyroid tissue increased expression of TGF-a, a growth factor, and EGFR, its receptor, results in aggressive proliferation and further downregulation of vitamin D receptors, which act to suppress hormone secretions. [25] [8] [28] Furthermore, the proliferative marker, Ki67 is seen to be highly expressed in the secondary nodular hyperplastic state. [28] [25] Tumour suppressor genes have also been highlighted as being silenced or degraded in nodular hyperplastic parathyroid tissue. [8] [28] One such gene, p53, has been shown to regulate multiple tumour suppressor pathways and in tumorigenesis can be degraded by b-catenin. This pathway, in some aspect, is mediated by CACYBP, which is highly expressed in nodular parathyroid hyperplasia. [28]
Early pharmaceutical treatment for tertiary hyperparathyroidism may include supplementing vitamin D and the use of cinacalcet. [4] [1] [29] Cinacalcet acts to increase the sensitivity of the calcium sensing receptors to calcium leading to a reduction in parathyroid hormone release, however, its use has limited impact in those with tertiary hyperparathyroidism. [29] These treatments are more likely only transient therapies before parathyroidectomy is performed. Indications for surgery in tertiary hyperparathyroidism commonly involve the development of chronic, severe conditions including osteopenia, persistent severe hypercalcemia, bone pain and pathologic fracture. [7] [2] [1] [4] Other indications include development of conditions such calciphylaxis. [1] Surgical options for tertiary hyperparathyroidism include subtotal parathyroidectomy (three and one half of total tissue) and total parathyroidectomy with autotransplantation of resected tissue. [7] [2] [1] Outcomes from surgery are generally favourable and a return to normalised blood calcium levels and parathyroid function is seen. [1]
In 1962, Dr C.E Dent reported that autonomous hyperparathyroidism may result from malabsorption syndromes and chronic kidney disease. [6] The term 'tertiary hyperparathyroidism' was first used in 1963 by Dr Walter St. Gaur to describe a case reported on at Massachusetts General hospital. [6] This case involved a patient who had presented with autonomous parathyroid adenoma causing hypercalcemia with a background of parathyroid hyperplasia. Further reports were recorded in 1964, 65 and 67 of suspected tertiary hyperparathyroidism.[ citation needed ]
In 1968 Davies, Dent and Watson produced a historic case study where they reviewed 200 cases of previously diagnosed primary hyperparathyroidism and found the majority of these cases should be reclassified as tertiary. [6] These were important findings as it allowed an understanding into distinguishing features of primary, secondary and tertiary hyperparathyroidism which then allows appropriate medical treatment.[ citation needed ]
It is now understood that tertiary hyperparathyroidism is defined as the presence of hypercalcemia, hyperphosphatemia and parathyroid hormone due to terminally biased parathyroid-bone-kidney feedback loop. [4] Although there is still conjecture as to whether tertiary hyperparathyroidism is also due to adenomatous growth or hyperplasia it is clear that tertiary hyperparathyroidism presents with some form of tissue enlargement in all four parathyroid glands. [7] [24]
Parathyroid glands are small endocrine glands in the neck of humans and other tetrapods. Humans usually have four parathyroid glands, located on the back of the thyroid gland in variable locations. The parathyroid gland produces and secretes parathyroid hormone in response to a low blood calcium, which plays a key role in regulating the amount of calcium in the blood and within the bones.
Parathyroid hormone (PTH), also called parathormone or parathyrin, is a peptide hormone secreted by the parathyroid glands that regulates the serum calcium concentration through its effects on bone, kidney, and intestine.
Calcium metabolism is the movement and regulation of calcium ions (Ca2+) in (via the gut) and out (via the gut and kidneys) of the body, and between body compartments: the blood plasma, the extracellular and intracellular fluids, and bone. Bone acts as a calcium storage center for deposits and withdrawals as needed by the blood via continual bone remodeling.
Hypercalcemia, also spelled hypercalcaemia, is a high calcium (Ca2+) level in the blood serum. The normal range is 2.1–2.6 mmol/L (8.8–10.7 mg/dL, 4.3–5.2 mEq/L), with levels greater than 2.6 mmol/L defined as hypercalcemia. Those with a mild increase that has developed slowly typically have no symptoms. In those with greater levels or rapid onset, symptoms may include abdominal pain, bone pain, confusion, depression, weakness, kidney stones or an abnormal heart rhythm including cardiac arrest.
Disorders of calcium metabolism occur when the body has too little or too much calcium. The serum level of calcium is closely regulated within a fairly limited range in the human body. In a healthy physiology, extracellular calcium levels are maintained within a tight range through the actions of parathyroid hormone, vitamin D and the calcium sensing receptor. Disorders in calcium metabolism can lead to hypocalcemia, decreased plasma levels of calcium or hypercalcemia, elevated plasma calcium levels.
Parathyroid chief cells are one of the two cell types of the parathyroid glands, along with oxyphil cells. The chief cells are much more prevalent in the parathyroid gland than the oxyphil cells. It is perceived that oxyphil cells may be derived from chief cells at puberty, as they are not present at birth like chief cells.
Hypoparathyroidism is decreased function of the parathyroid glands with underproduction of parathyroid hormone (PTH). This can lead to low levels of calcium in the blood, often causing cramping and twitching of muscles or tetany, and several other symptoms. It is a very rare disease. The condition can be inherited, but it is also encountered after thyroid or parathyroid gland surgery, and it can be caused by immune system-related damage as well as a number of rarer causes. The diagnosis is made with blood tests, and other investigations such as genetic testing depending on the results. The primary treatment of hypoparathyroidism is calcium and vitamin D supplementation. Calcium replacement or vitamin D can ameliorate the symptoms but can increase the risk of kidney stones and chronic kidney disease. Additionally, medications such as recombinant human parathyroid hormone or teriparatide may be given by injection to replace the missing hormone.
Hyperparathyroidism is an increase in parathyroid hormone (PTH) levels in the blood. This occurs from a disorder either within the parathyroid glands or as response to external stimuli.
Parathyroidectomy is the surgical removal of one or more of the (usually) four parathyroid glands. This procedure is used to remove an adenoma or hyperplasia of these glands when they are producing excessive parathyroid hormone (PTH): hyperparathyroidism. The glands are usually four in number and located adjacent to the posterior surface of the thyroid gland, but their exact location is variable. When an elevated PTH level is found, a sestamibi scan or an ultrasound may be performed in order to confirm the presence and location of abnormal parathyroid tissue.
Cinacalcet, sold under the brand name Sensipar among others, is a medication used to treat primary hyperparathyroidism, tertiary hyperparathyroidism and parathyroid carcinoma. Cinacalcet acts as a calcimimetic by allosteric activation of the calcium-sensing receptor that is expressed in various human organ tissues.
Renal osteodystrophy is currently defined as an alteration of bone morphology in patients with chronic kidney disease (CKD). It is one measure of the skeletal component of the systemic disorder of chronic kidney disease-mineral and bone disorder (CKD-MBD). The term "renal osteodystrophy" was coined in 1943, 60 years after an association was identified between bone disease and kidney failure.
Primary hyperparathyroidism is a medical condition where the parathyroid gland produce excess amounts of parathyroid hormone (PTH). The symptoms of the condition relate to the resulting elevated serum calcium (hypercalcemia), which can cause digestive symptoms, kidney stones, psychiatric abnormalities, and bone disease.
Osteitis fibrosa cystica is a skeletal disorder resulting in a loss of bone mass, a weakening of the bones as their calcified supporting structures are replaced with fibrous tissue, and the formation of cyst-like brown tumors in and around the bone. Osteitis fibrosis cystica (OFC), also known as osteitis fibrosa, osteodystrophia fibrosa, and von Recklinghausen's disease of bone, is caused by hyperparathyroidism, which is a surplus of parathyroid hormone from over-active parathyroid glands. This surplus stimulates the activity of osteoclasts, cells that break down bone, in a process known as osteoclastic bone resorption. The hyperparathyroidism can be triggered by a parathyroid adenoma, hereditary factors, parathyroid carcinoma, or renal osteodystrophy. Osteoclastic bone resorption releases minerals, including calcium, from the bone into the bloodstream, causing both elevated blood calcium levels, and the structural changes which weaken the bone. The symptoms of the disease are the consequences of both the general softening of the bones and the excess calcium in the blood, and include bone fractures, kidney stones, nausea, moth-eaten appearance in the bones, appetite loss, and weight loss.
Secondary hyperparathyroidism is the medical condition of excessive secretion of parathyroid hormone (PTH) by the parathyroid glands in response to hypocalcemia, with resultant hyperplasia of these glands. This disorder is primarily seen in patients with chronic kidney failure. It is sometimes abbreviated "SHPT" in medical literature.
Milk-alkali syndrome (MAS), also referred to as calcium-alkali syndrome, is the third most common cause of hypercalcemia. Milk-alkali syndrome is characterized by elevated blood calcium levels, metabolic alkalosis, and acute kidney injury.
A parathyroid adenoma is a benign tumor of the parathyroid gland. It generally causes hyperparathyroidism; there are very few reports of parathyroid adenomas that were not associated with hyperparathyroidism.
Many conditions are associated with disorders of the function of the parathyroid gland. Some disorders may be purely anatomical resulting in an enlarged gland which will raise concern. Such benign disorders, such as parathyroid cyst, are not discussed here. Parathyroid diseases can be divided into those causing hyperparathyroidism, and those causing hypoparathyroidism.
Familial hypocalciuric hypercalcemia (FHH) is an inherited condition that can cause hypercalcemia, a serum calcium level typically above 10.2 mg/dL; although uncommon. It is also known as familial benign hypocalciuric hypercalcemia (FBHH) where there is usually a family history of hypercalcemia which is mild, a urine calcium to creatinine ratio <0.01, and urine calcium <200 mg/day.
A calcimimetic is a pharmaceutical drug that mimics the action of calcium on tissues, by allosteric activation of the calcium-sensing receptor that is expressed in various human organ tissues. Calcimimetics are used to treat secondary hyperparathyroidism (SHPT).
A sestamibi parathyroid scan is a procedure in nuclear medicine which is performed to localize parathyroid adenoma, which causes Hyperparathyroidism. Adequate localization of parathyroid adenoma allows the surgeon to use a minimally invasive surgical approach.
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