Parathyroid hormone

Last updated

PTH
Available structures
PDB Ortholog search: PDBe RCSB
Identifiers
Aliases PTH , PTH1, parathyroid hormone, Parathyroid hormone, FIH1
External IDs OMIM: 168450 MGI: 97799 HomoloGene: 266 GeneCards: PTH
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_000315
NM_001316352

NM_020623

RefSeq (protein)

NP_000306
NP_001303281

NP_065648

Location (UCSC) Chr 11: 13.49 – 13.5 Mb Chr 7: 112.98 – 112.99 Mb
PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

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. [5]

PTH influences bone remodeling, which is an ongoing process in which bone tissue is alternately resorbed and rebuilt over time. PTH is secreted in response to low blood serum calcium (Ca2+) levels. PTH indirectly stimulates osteoclast activity within the bone matrix (osteon), in an effort to release more ionic calcium (Ca2+) into the blood to elevate a low serum calcium level. The bones act as a (metaphorical) "bank of calcium" from which the body can make "withdrawals" as needed to keep the amount of calcium in the blood at appropriate levels despite the ever-present challenges of metabolism, stress, and nutritional variations. PTH is "a key that unlocks the bank vault" to remove the calcium.

PTH is secreted primarily by the chief cells of the parathyroid glands. The gene for PTH is located on chromosome 11. It is a polypeptide containing 84 amino acids, which is a prohormone. It has a molecular mass around 9500 Da. [6] Its action is opposed by the hormone calcitonin.

There are two types of PTH receptors. Parathyroid hormone 1 receptors, activated by the 34 N-terminal amino acids of PTH, are present at high levels on the cells of bone and kidney. Parathyroid hormone 2 receptors are present at high levels on the cells of central nervous system, pancreas, testes, and placenta. [7] The half-life of PTH is about 4 minutes. [8]

Disorders that yield too little or too much PTH, such as hypoparathyroidism, hyperparathyroidism, and paraneoplastic syndromes can cause bone disease, hypocalcemia, and hypercalcemia.

Structure

hPTH-(1-84) crystallizes as a slightly bent, long, helical dimer. The extended helical conformation of hPTH-(1-84) is the likely bioactive conformation. [9] The N-terminal fragment 1-34 of parathyroid hormone (PTH) has been crystallized and the structure has been refined to 0.9 Å resolution.

helical dimer structure of hPTH-(1-34) The ribbon cartoon structure.png
helical dimer structure of hPTH-(1-34)

Function

Regulation of serum calcium

The parathyroid gland releases PTH which keeps calcium in homeostasis. Parathyroid Hormone Negative Feedback.svg
The parathyroid gland releases PTH which keeps calcium in homeostasis.
A diagrammatic representation of the movements of calcium ions into and out of the blood plasma (the central square labeled PLASMA Ca ) in an adult in calcium balance:
The widths of the red arrows indicating movement into and out of the plasma are roughly in proportion to the daily amounts of calcium moved in the indicated directions.
The size of the central square in not in proportion to the size of the diagrammatic bone, which represents the calcium present in the skeleton, and contains about 25,000 mmol (or 1 kg) of calcium compared to the 9 mmol (360 mg) dissolved in the blood plasma.
The differently colored narrow arrows indicate where the specified hormones act, and their effects ("+" means stimulates; "-" means inhibits) when their plasma levels are high.
PTH is parathyroid hormone, 1,25 OH VIT D3 is calcitriol or 1,25 dihydroxyvitamin D3, and CALCITONIN is a hormone secreted by the thyroid gland when the plasma ionized calcium level is high or rising.
The diagram does not show the extremely small amounts of calcium that move into and out of the cells of the body, nor does it indicate the calcium that is bound to the extracellular proteins (in particular the plasma proteins) or to plasma phosphate. Calcium balance 2.jpg
A diagrammatic representation of the movements of calcium ions into and out of the blood plasma (the central square labeled PLASMA Ca ) in an adult in calcium balance:
The widths of the red arrows indicating movement into and out of the plasma are roughly in proportion to the daily amounts of calcium moved in the indicated directions.
The size of the central square in not in proportion to the size of the diagrammatic bone, which represents the calcium present in the skeleton, and contains about 25,000 mmol (or 1 kg) of calcium compared to the 9 mmol (360 mg) dissolved in the blood plasma.
The differently colored narrow arrows indicate where the specified hormones act, and their effects (“+” means stimulates; “-“ means inhibits) when their plasma levels are high.
PTH is parathyroid hormone, 1,25 OH VIT D3 is calcitriol or 1,25 dihydroxyvitamin D3, and CALCITONIN is a hormone secreted by the thyroid gland when the plasma ionized calcium level is high or rising.
The diagram does not show the extremely small amounts of calcium that move into and out of the cells of the body, nor does it indicate the calcium that is bound to the extracellular proteins (in particular the plasma proteins) or to plasma phosphate.

Parathyroid hormone regulates serum calcium through its effects on bone, kidney, and the intestine: [5]

In bone, PTH enhances the release of calcium from the large reservoir contained in the bones. [16] Bone resorption is the normal destruction of bone by osteoclasts, which are indirectly stimulated by PTH. Stimulation is indirect since osteoclasts do not have a receptor for PTH; rather, PTH binds to osteoblasts, the cells responsible for creating bone. Binding stimulates osteoblasts to increase their expression of RANKL and inhibits their secretion of osteoprotegerin (OPG). Free OPG competitively binds to RANKL as a decoy receptor, preventing RANKL from interacting with RANK, a receptor for RANKL. The binding of RANKL to RANK (facilitated by the decreased amount of OPG available for binding the excess RANKL) stimulates osteoclast precursors, which are of a monocyte lineage, to fuse. The resulting multinucleated cells are osteoclasts, which ultimately mediate bone resorption. Estrogen also regulates this pathway through its effects on PTH. Estrogen suppresses T cell TNF production by regulating T cell differentiation and activity in the bone marrow, thymus, and peripheral lymphoid organs. In the bone marrow, estrogen downregulates the proliferation of hematopoietic stem cells through an IL-7 dependent mechanism. [17]

In the kidney, around 250 mmol of calcium ions are filtered into the glomerular filtrate per day. Most of this (245 mmol/d) is reabsorbed from the tubular fluid, leaving about 5 mmol/d to be excreted in the urine. This reabsorption occurs throughout the tubule (most, 60-70%, of it in the proximal tubule), except in the thin segment of the loop of Henle. [11] Circulating parathyroid hormone only influences the reabsorption that occurs in the distal tubules and the renal collecting ducts [11] (but see Footnote [nb 1] ). A more important effect of PTH on the kidney is, however, its inhibition of the reabsorption of phosphate (HPO42−) from the tubular fluid, resulting in a decrease in the plasma phosphate concentration. Phosphate ions form water-insoluble salts with calcium. Thus, a decrease in the phosphate concentration of the blood plasma (for a given total calcium concentration) increases the amount of calcium that is ionized. [20] [21] A third important effect of PTH on the kidney is its stimulation of the conversion of 25-hydroxy vitamin D into 1,25-dihydroxy vitamin D (calcitriol), which is released into the circulation. This latter form of vitamin D is the active hormone which stimulates calcium uptake from the intestine. [22]

Via the kidney, PTH enhances the absorption of calcium in the intestine by increasing the production of activated vitamin D. Vitamin D activation occurs in the kidney. PTH up-regulates 25-hydroxyvitamin D3 1-alpha-hydroxylase, the enzyme responsible for 1-alpha hydroxylation of 25-hydroxy vitamin D, converting vitamin D to its active form (1,25-dihydroxy vitamin D). This activated form of vitamin D increases the absorption of calcium (as Ca2+ ions) by the intestine via calbindin.

PTH was one of the first hormones to be shown to use the G-protein adenylyl cyclase second messenger system.

Regulation of serum phosphate

PTH reduces the reabsorption of phosphate from the proximal tubule of the kidney, [23] which means more phosphate is excreted through the urine.

However, PTH enhances the uptake of phosphate from the intestine and bones into the blood. In the bone, slightly more calcium than phosphate is released from the breakdown of bone. In the intestines, absorption of both calcium and phosphate is mediated by an increase in activated vitamin D. The absorption of phosphate is not as dependent on vitamin D as is that of calcium. The result of PTH release is a small net drop in the serum concentration of phosphate.

Vitamin D synthesis

PTH upregulates the activity of 1-α-hydroxylase enzyme, which converts 25-hydroxycholecalciferol, the major circulating form of inactive vitamin D, into 1,25-dihydroxycholecalciferol, the active form of vitamin D, in the kidney.

Interactive pathway map

Click on genes, proteins and metabolites below to link to respective articles. [§ 1]

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VitaminDSynthesis WP1531.png Go to articleGo to articleGo to articleGo to articlego to articleGo to articleGo to articleGo to articlego to articlego to articlego to articlego to articleGo to articleGo to articlego to articleGo to articlego to articlego to articlego to articleGo to articlego to article
|alt=Vitamin D Synthesis Pathway (view / edit)]]
Vitamin D Synthesis Pathway (view / edit)
  1. The interactive pathway map can be edited at WikiPathways: "VitaminDSynthesis_WP1531".

Regulation of PTH secretion

Secretion of parathyroid hormone is determined chiefly by serum ionized calcium concentration through negative feedback. Parathyroid cells express calcium-sensing receptors on the cell surface. PTH is secreted when [Ca2+] is decreased (calcitonin is secreted when serum calcium levels are elevated). The G-protein-coupled calcium receptors bind extracellular calcium and may be found on the surface on a wide variety of cells distributed in the brain, heart, skin, stomach, C cells, and other tissues. In the parathyroid gland, high concentrations of extracellular calcium result in activation of the Gq G-protein coupled cascade through the action of phospholipase C. This hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) to liberate intracellular messengers IP3 and diacylglycerol (DAG). Ultimately, these two messengers result in a release of calcium from intracellular stores into the cytoplasmic space. Hence a high extracellular calcium concentration leads to an increase in the cytoplasmic calcium concentration. In contrast to the mechanism that most secretory cells use, this high cytoplasmic calcium concentration inhibits the fusion of vesicles containing granules of preformed PTH with the membrane of the parathyroid cell, and thus inhibits release of PTH.

In the parathyroids, magnesium serves this role in stimulus-secretion coupling. A mild decrease in serum magnesium levels stimulates the reabsorptive activity PTH has on the kidneys. Severe hypomagnesemia inhibits PTH secretion and also causes resistance to PTH, leading to a form of hypoparathyroidism that is reversible. [24]

Stimulators

Inhibitors

Disorders

Hyperparathyroidism, the presence of excessive amounts of parathyroid hormone in the blood, occurs in two very distinct sets of circumstances. Primary hyperparathyroidism is due to autonomous, abnormal hypersecretion of PTH from the parathyroid gland, while secondary hyperparathyroidism is an appropriately high PTH level seen as a physiological response to hypocalcemia. A low level of PTH in the blood is known as hypoparathyroidism and is most commonly due to damage to or removal of parathyroid glands during thyroid surgery.

There are a number of rare but well-described genetic conditions affecting parathyroid hormone metabolism, including pseudohypoparathyroidism, familial hypocalciuric hypercalcemia, and autosomal dominant hypercalciuric hypocalcemia. Of note, PTH is unchanged in pseudopseudohypoparathyroidism. In osteoporotic women, administration of an exogenous parathyroid hormone analogue (teriparatide, by daily injection) superimposed on estrogen therapy produced increases in bone mass and reduced vertebral and nonvertebral fractures by 45 to 65%. [28]

Measurement

PTH can be measured in the blood in several different forms: intact PTH; N-terminal PTH; mid-molecule PTH, and C-terminal PTH, and different tests are used in different clinical situations. The level may be stated in pg/dL or pmol/L (sometimes abbreviated mmol/L); multiply by 0.1060 to convert from pg/dL to pmol/L. [29]

A US source states the average PTH level to be 8–51 pg/mL. [30] In the UK the biological reference range is considered to be 1.6-6.9 pmol/L. [31] Normal total plasma calcium level ranges from 8.5 to 10.2 mg/dL (2.12 mmol/L to 2.55 mmol/L). [32]

Interpretive guide

The intact PTH and calcium normal ranges are different for age; calcium is also different for sex. [33] [34]

ConditionIntact PTHCalcium
Normal ParathyroidNormalNormal
Hypoparathyroidism Low or Low Normal [note 1] Low
Hyperparathyroidism
- Primary High or Normal [note 1] High
- Secondary HighNormal or Low
- Tertiary [note 2] HighHigh
Non-Parathyroid Hypercalcemia Low or Low Normal [note 1] High
  1. 1 2 3 Low Normal or Normal only for Quest Lab, not LabCorp
  2. Both primary and tertiary hyperparathyroidism may have high PTH and high calcium. Tertiary is differentiated from primary hyperparathyroidism by a history of chronic kidney failure and secondary hyperparathyroidism.

Medical uses

Recombinant human parathyroid hormone


Recombinant human parathyroid hormone, sold under the brand name Preotact among others, is an artificially manufactured form of the parathyroid hormone used to treat hypoparathyroidism (under-active parathyroid glands). [35] [36] [37] [38] Recombinant human parathyroid hormone is used in the treatment of osteoporosis in postmenopausal women at high risk of osteoporotic fractures. [39] A significant reduction in the incidence of vertebral fractures has been demonstrated. [39] It is used in combination with calcium and vitamin D supplements. [35] [37]

The most common side effects include sensations of tingling, tickling, pricking, or burning of the skin (paraesthesia); low blood calcium; headache; high blood calcium; and nausea. [36]

Recombinant human parathyroid hormone (Preotact) was approved for medical use in the European Union in April 2006. [39] Recombinant human parathyroid hormone (Natpara) was approved for medical use in the United States in January 2015, and in the European Union (as Natpar) in February 2017. [37] [40]

Teriparatide

Teriparatide structure.svg


Parathyroid hormone
Teriparatide structure.svg
Clinical data
Trade names Forteo, Forsteo
Biosimilars Bonsity, [41] Kauliv, [42] Livogiva, [43] Osnuvo, [44] Qutavina, [45] Sondelbay, [46] Teribone, [47]
AHFS/Drugs.com Monograph
MedlinePlus a603018
License data
Pregnancy
category
Routes of
administration
Subcutaneous
ATC code
Legal status
Legal status
Pharmacokinetic data
Bioavailability 95%
Metabolism Liver (nonspecific proteolysis)
Elimination half-life Subcutaneous: 1 hour
Excretion Kidney (metabolites)
Identifiers
CAS Number
PubChem CID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEMBL
Chemical and physical data
Formula C181H291N55O51S2
Molar mass 4117.77 g·mol−1
3D model (JSmol)
  • [H]/N=C(\N)/NCCC[C@@H](C(=O)N[C@@H](C(C)C)C(=O)N[C@@H](CCC(=O)O)C(=O)N[C@@H](Cc1c[nH]c2c1cccc2)C(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](CCCN/C(=N/[H])/N)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](CCC(=O)N)C(=O)N[C@@H](CC(=O)O)C(=O)N[C@@H](C(C)C)C(=O)N[C@@H](Cc3cnc[nH]3)C(=O)N[C@@H](CC(=O)N)C(=O)N[C@@H](Cc4ccccc4)C(=O)O)NC(=O)[C@H](CCC(=O)O)NC(=O)[C@H](CCSC)NC(=O)[C@H](CO)NC(=O)[C@H](CC(=O)N)NC(=O)[C@H](CC(C)C)NC(=O)[C@H](Cc5cnc[nH]5)NC(=O)[C@H](CCCCN)NC(=O)CNC(=O)[C@H](CC(C)C)NC(=O)[C@H](CC(=O)N)NC(=O)[C@H](Cc6cnc[nH]6)NC(=O)[C@H](CCSC)NC(=O)[C@H](CC(C)C)NC(=O)[C@H](CCC(=O)N)NC(=O)[C@H]([C@@H](C)CC)NC(=O)[C@H](CCC(=O)O)NC(=O)[C@H](CO)NC(=O)[C@H](C(C)C)NC(=O)[C@H](CO)N
  • InChI=1S/C181H291N55O51S2/c1-21-96(18)146(236-160(267)114(48-53-141(250)251)212-174(281)132(84-239)232-177(284)143(93(12)13)233-147(254)103(185)82-237)178(285)216-111(45-50-134(187)241)155(262)219-119(65-90(6)7)163(270)213-116(55-62-289-20)158(265)224-124(71-100-79-196-86-203-100)167(274)226-126(73-135(188)242)169(276)217-117(63-88(2)3)148(255)201-81-138(245)205-105(39-27-30-56-182)149(256)223-123(70-99-78-195-85-202-99)166(273)221-121(67-92(10)11)164(271)225-128(75-137(190)244)171(278)231-131(83-238)173(280)214-115(54-61-288-19)157(264)210-112(46-51-139(246)247)153(260)208-109(43-34-60-199-181(193)194)159(266)234-144(94(14)15)175(282)215-113(47-52-140(248)249)156(263)222-122(69-98-77-200-104-38-26-25-37-102(98)104)165(272)220-120(66-91(8)9)161(268)209-108(42-33-59-198-180(191)192)151(258)206-106(40-28-31-57-183)150(257)207-107(41-29-32-58-184)152(259)218-118(64-89(4)5)162(269)211-110(44-49-133(186)240)154(261)228-129(76-142(252)253)172(279)235-145(95(16)17)176(283)229-125(72-101-80-197-87-204-101)168(275)227-127(74-136(189)243)170(277)230-130(179(286)287)68-97-35-23-22-24-36-97/h22-26,35-38,77-80,85-96,103,105-132,143-146,200,237-239H,21,27-34,39-76,81-84,182-185H2,1-20H3,(H2,186,240)(H2,187,241)(H2,188,242)(H2,189,243)(H2,190,244)(H,195,202)(H,196,203)(H,197,204)(H,201,255)(H,205,245)(H,206,258)(H,207,257)(H,208,260)(H,209,268)(H,210,264)(H,211,269)(H,212,281)(H,213,270)(H,214,280)(H,215,282)(H,216,285)(H,217,276)(H,218,259)(H,219,262)(H,220,272)(H,221,273)(H,222,263)(H,223,256)(H,224,265)(H,225,271)(H,226,274)(H,227,275)(H,228,261)(H,229,283)(H,230,277)(H,231,278)(H,232,284)(H,233,254)(H,234,266)(H,235,279)(H,236,267)(H,246,247)(H,248,249)(H,250,251)(H,252,253)(H,286,287)(H4,191,192,198)(H4,193,194,199)/t96-,103-,105-,106-,107-,108-,109-,110-,111-,112-,113-,114-,115-,116-,117-,118-,119-,120-,121-,122-,123-,124-,125-,126-,127-,128-,129-,130-,131-,132-,143-,144-,145-,146-/m0/s1 X mark.svgN
  • Key:OGBMKVWORPGQRR-UMXFMPSGSA-N X mark.svgN
 X mark.svgNYes check.svgY  (what is this?)    (verify)
Teriparatide, sold under the brand name Forteo, is a form of parathyroid hormone (PTH) consisting of the first (N-terminus) 34 amino acids, which is the bioactive portion of the hormone. [50] It is an effective anabolic (promoting bone formation) agent [52] used in the treatment of some forms of osteoporosis. [50] [53] Teriparatide is a recombinant human parathyroid hormone analog (PTH 1-34). [50] It has an identical sequence to the 34 N-terminal amino acids of the 84-amino acid human parathyroid hormone. [50]

See also

Footnote

  1. This reduction in the rate of calcium excretion via the urine is a minor effect of high parathyroid hormone levels in the blood. The main determinant of the amount of calcium excreted into the urine per day is the plasma ionized calcium concentration itself. The plasma parathyroid hormone (PTH) concentration only increases or decreases the amount of calcium excreted at any specified plasma ionized calcium concentration. Thus, in primary hyperparathyroidism, the quantity of calcium excreted in the urine per day is increased despite the high levels of PTH in the blood, because hyperparathyroidism results in hypercalcemia, which increases the urinary calcium concentration (hypercalcuria) despite the moderately increased rate of calcium reabsorption from the renal tubular fluid caused by PTH's direct effect on those tubules. Renal stones are, therefore, often a first indication of hyperparathyroidism, especially since the hypercalcuria is accompanied by an increase in urinary phosphate excretion (a direct result of the high plasma PTH levels). Together the calcium and phosphate tend to precipitate out as water-insoluble salts, which readily form solid "stones". [11] [18] [19]

Related Research Articles

<span class="mw-page-title-main">Parathyroid gland</span> Endocrine gland

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.

<span class="mw-page-title-main">Calcium metabolism</span> Movement and regulation of calcium ions in and out of the body

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.

<span class="mw-page-title-main">Calcitonin</span> Amino acid peptide hormone secreted by the thyroid gland

Calcitonin is a 32 amino acid peptide hormone secreted by parafollicular cells (also known as C cells) of the thyroid (or endostyle) in humans and other chordates in the ultimopharyngeal body. It acts to reduce blood calcium (Ca2+), opposing the effects of parathyroid hormone (PTH).

<span class="mw-page-title-main">Hypocalcemia</span> Low calcium levels in ones blood serum

Hypocalcemia is a medical condition characterized by low calcium levels in the blood serum. The normal range of blood calcium is typically between 2.1–2.6 mmol/L, while levels less than 2.1 mmol/L are defined as hypocalcemic. Mildly low levels that develop slowly often have no symptoms. Otherwise symptoms may include numbness, muscle spasms, seizures, confusion, or in extreme cases cardiac arrest.

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.

<span class="mw-page-title-main">Parathyroid chief cell</span>

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.

<span class="mw-page-title-main">Hyperparathyroidism</span> Increase in parathyroid hormone levels in the blood

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.

<span class="mw-page-title-main">Teriparatide</span> Pharmaceutical drug for treating osteoporosis

Teriparatide, sold under the brand name Forteo, is a form of parathyroid hormone (PTH) consisting of the first (N-terminus) 34 amino acids, which is the bioactive portion of the hormone. It is an effective anabolic agent used in the treatment of some forms of osteoporosis. Teriparatide is a recombinant human parathyroid hormone analog. It has an identical sequence to the 34 N-terminal amino acids of the 84-amino acid human parathyroid hormone.

<span class="mw-page-title-main">Parathyroidectomy</span> Surgical removal of one or more of the parathyroid glands

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.

<span class="mw-page-title-main">Cinacalcet</span> Chemical compound

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.

<span class="mw-page-title-main">Calcitriol</span> Active form of vitamin D

Calcitriol is the active form of vitamin D, normally made in the kidney. It is also known as 1,25-dihydroxycholecalciferol. It is a hormone which binds to and activates the vitamin D receptor in the nucleus of the cell, which then increases the expression of many genes. Calcitriol increases blood calcium (Ca2+) mainly by increasing the uptake of calcium from the intestines.

<span class="mw-page-title-main">Osteitis fibrosa cystica</span> Medical condition

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.

<span class="mw-page-title-main">Bone resorption</span> Medical condition

Bone resorption is resorption of bone tissue, that is, the process by which osteoclasts break down the tissue in bones and release the minerals, resulting in a transfer of calcium from bone tissue to the blood.

<span class="mw-page-title-main">Secondary hyperparathyroidism</span> Medical condition

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.

<span class="mw-page-title-main">Tertiary hyperparathyroidism</span> Medical condition

Tertiary hyperparathyroidism is a condition involving the overproduction of the hormone, parathyroid hormone, produced by the parathyroid glands. 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, secondary and tertiary are thought to result due to chronic kidney disease (CKD). 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. Tertiary hyperparathyroidism was first described in the late 1960s and had been misdiagnosed as primary prior to this. 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. Upon diagnosis treatment of tertiary hyperparathyroidism usually leads to a surgical intervention.

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.

Recombinant human parathyroid hormone, sold under the brand name Preotact among others, is an artificially manufactured form of the parathyroid hormone used to treat hypoparathyroidism. Recombinant human parathyroid hormone is used in the treatment of osteoporosis in postmenopausal women at high risk of osteoporotic fractures. A significant reduction in the incidence of vertebral fractures has been demonstrated. It is used in combination with calcium and vitamin D supplements.

<span class="mw-page-title-main">Etelcalcetide</span> Chemical compound

Etelcalcetide is a calcimimetic drug for the treatment of secondary hyperparathyroidism in patients undergoing hemodialysis. It is administered intravenously at the end of each dialysis session. Etelcalcetide functions by binding to and activating the calcium-sensing receptor in the parathyroid gland. Parsabiv is currently owned by Amgen and Ono Pharmaceuticals in Japan.

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Further reading