Parathyroid hormone

Parathyroid hormone (PTH), or parathormone, is secreted by the parathyroid glands as a polypeptide containing 84 amino acids. It acts to increase the concentration of calcium (Ca2+) in the blood, whereas calcitonin (a hormone produced by the parafollicular cells (C cells) of the thyroid gland) acts to decrease calcium concentration.PTH acts to increase the concentration of calcium in the blood by acting upon parathyroid hormone receptor in three parts of the body: [GeorgiaPhysiology|5/5ch6/s5ch6_11]

Functions

Effects on serum calcium (raising)

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

Normal total plasma calcium level is 9.4mg/dl(8-11) or 2.4mmol/L [guyton] http://books.google.com/books?id=BxLU6XhZsTAC&pg=RA1-PA281&lpg=RA1-PA281&dq=pth+second+messenger&source=web&ots=5awUECyZo-&sig=EhEGbV9WdI2Xp5Sv5eJQJ_63S3U#PRA1-PA281,M1] .

Effects on serum phosphate (decrease, with compensation)

PTH reduces the reabsorption of phosphate from the proximal tubule of the kidney ] 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, which 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 end result is a small net drop in the serum concentration of phosphate.

Feedback regulation

Increased calcium concentration in the blood acts (via feedback inhibition) to decrease PTH secretion by the parathyroid glands.

This is achieved by the activation of calcium-sensing receptors located on parathyroid cells. [GeorgiaPhysiology|5/5ch6/s5ch6_9]

yndromes

* A high level of PTH in the blood is known as hyperparathyroidism.
** If the cause is in the parathyroid gland it is called "primary hyperparathyroidism". The causes are parathyroid adenoma, parathyroid hyperplasia and parathyroid cancer.
** If the cause is outside the gland, it is known as "secondary hyperparathyroidism". This can occur in chronic renal failure.

* A low level of PTH in the blood is known as hypoparathyroidism. Causes include surgical misadventure ("eg" inadvertent removal during routine thyroid surgery), autoimmune disorder, and inborn errors of metabolism.

Measurements

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.

References

ee also

* Calcium metabolism
* Disorders of calcium metabolism
* Parathyroid hormone-related protein

Further reading

PBB_Further_reading
citations =
*cite journal | author=Drüeke TB, Massy ZA |title=Advanced oxidation protein products, parathyroid hormone and vascular calcification in uremia |journal=Blood Purif. |volume=20 |issue= 5 |pages= 494–7 |year= 2003 |pmid= 12207101 |doi=
*cite journal | author=Parfitt AM |title=Parathyroid hormone and periosteal bone expansion |journal=J. Bone Miner. Res. |volume=17 |issue= 10 |pages= 1741–3 |year= 2003 |pmid= 12369776 |doi=
*cite journal | author=Martin TJ |title=Does bone resorption inhibition affect the anabolic response to parathyroid hormone? |journal=Trends Endocrinol. Metab. |volume=15 |issue= 2 |pages= 49–50 |year= 2004 |pmid= 15080150 |doi=
*cite journal | author=Keutmann HT, Sauer MM, Hendy GN, "et al." |title=Complete amino acid sequence of human parathyroid hormone |journal=Biochemistry |volume=17 |issue= 26 |pages= 5723–9 |year= 1979 |pmid= 728431 |doi=
*cite journal | author=Keutmann HT, Niall HD, O'Riordan JL, Potts JT |title=A reinvestigation of the amino-terminal sequence of human parathyroid hormone |journal=Biochemistry |volume=14 |issue= 9 |pages= 1842–7 |year= 1975 |pmid= 1125201| doi=10.1021/bi00680a006
*cite journal | author=Parkinson DB, Thakker RV |title=A donor splice site mutation in the parathyroid hormone gene is associated with autosomal recessive hypoparathyroidism |journal=Nat. Genet. |volume=1 |issue= 2 |pages= 149–52 |year= 1993 |pmid= 1302009 |doi= 10.1038/ng0592-149
*cite journal | author=Handt O, Reis A, Schmidtke J |title=Ectopic transcription of the parathyroid hormone gene in lymphocytes, lymphoblastoid cells and tumour tissue |journal=J. Endocrinol. |volume=135 |issue= 2 |pages= 249–56 |year= 1993 |pmid= 1474331 |doi=
*cite journal | author=Tonoki H, Narahara K, Matsumoto T, Niikawa N |title=Regional mapping of the parathyroid hormone gene (PTH) by cytogenetic and molecular studies |journal=Cytogenet. Cell Genet. |volume=56 |issue= 2 |pages= 103–4 |year= 1991 |pmid= 1672845 |doi=
*cite journal | author=Klaus W, Dieckmann T, Wray V, "et al." |title=Investigation of the solution structure of the human parathyroid hormone fragment (1-34) by 1H NMR spectroscopy, distance geometry, and molecular dynamics calculations |journal=Biochemistry |volume=30 |issue= 28 |pages= 6936–42 |year= 1991 |pmid= 2069952| doi=10.1021/bi00242a018
*cite journal | author=Arnold A, Horst SA, Gardella TJ, "et al." |title=Mutation of the signal peptide-encoding region of the preproparathyroid hormone gene in familial isolated hypoparathyroidism |journal=J. Clin. Invest. |volume=86 |issue= 4 |pages= 1084–7 |year= 1990 |pmid= 2212001| doi=10.1172/JCI114811
*cite journal | author=Nussbaum SR, Gaz RD, Arnold A |title=Hypercalcemia and ectopic secretion of parathyroid hormone by an ovarian carcinoma with rearrangement of the gene for parathyroid hormone |journal=N. Engl. J. Med. |volume=323 |issue= 19 |pages= 1324–8 |year= 1990 |pmid= 2215618 |doi=
*cite journal | author=Ahn TG, Antonarakis SE, Kronenberg HM, "et al." |title=Familial isolated hypoparathyroidism: a molecular genetic analysis of 8 families with 23 affected persons |journal=Medicine (Baltimore) |volume=65 |issue= 2 |pages= 73–81 |year= 1986 |pmid= 3005800 |doi=
*cite journal | author=Tregear GW, van Rietschoten J, Greene E, "et al." |title=Solid-phase synthesis of the biologically active N-terminal 1 - 34 peptide of human parathyroid hormone |journal=Hoppe-Seyler's Z. Physiol. Chem. |volume=355 |issue= 4 |pages= 415–21 |year= 1975 |pmid= 4474131 |doi=
*cite journal | author=Niall HD, Sauer RT, Jacobs JW, "et al." |title=The amino-acid sequence of the amino-terminal 37 residues of human parathyroid hormone |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=71 |issue= 2 |pages= 384–8 |year= 1974 |pmid= 4521809| doi=10.1073/pnas.71.2.384
*cite journal | author=Andreatta RH, Hartmann A, Jöhl A, "et al." |title= [Synthesis of sequence 1-34 of human parathyroid hormone] |journal=Helv. Chim. Acta |volume=56 |issue= 1 |pages= 470–3 |year= 1973 |pmid= 4721748 |doi= 10.1002/hlca.19730560139
*cite journal | author=Jacobs JW, Kemper B, Niall HD, "et al." |title=Structural analysis of human proparathyroid hormone by a new microsequencing approach |journal=Nature |volume=249 |issue= 453 |pages= 155–7 |year= 1974 |pmid= 4833516| doi=10.1038/249155a0
*cite journal | author=Vasicek TJ, McDevitt BE, Freeman MW, "et al." |title=Nucleotide sequence of the human parathyroid hormone gene |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=80 |issue= 8 |pages= 2127–31 |year= 1983 |pmid= 6220408| doi=10.1073/pnas.80.8.2127
*cite journal | author=Mayer H, Breyel E, Bostock C, Schmidtke J |title=Assignment of the human parathyroid hormone gene to chromosome 11 |journal=Hum. Genet. |volume=64 |issue= 3 |pages= 283–5 |year= 1983 |pmid= 6885073| doi=10.1007/BF00279412
*cite journal | author=Hendy GN, Kronenberg HM, Potts JT, Rich A |title=Nucleotide sequence of cloned cDNAs encoding human preproparathyroid hormone |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=78 |issue= 12 |pages= 7365–9 |year= 1982 |pmid= 6950381 |doi=
*cite journal | author=Hendy GN, Bennett HP, Gibbs BF, "et al." |title=Proparathyroid hormone is preferentially cleaved to parathyroid hormone by the prohormone convertase furin. A mass spectrometric study |journal=J. Biol. Chem. |volume=270 |issue= 16 |pages= 9517–25 |year= 1995 |pmid= 7721880 |doi=

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