Calcitonin Chemische Eigenschaften,Einsatz,Produktion Methoden
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Beschreibung
Calcitonin has been approved for the treatment of postmenopausal
osteoporosis, hypercalcemia of malignancy, and Paget's disease of the bone.Several sources are available
(e.g., eel, human, salmon, and porcine). The calcitonin isolated from salmon is the preferred source, because it
has greater receptor affinity and a longer half-life than the human hormone.
Chemische Eigenschaften
Calcitonin is a single-chain polypeptide composed of 32
amino acid residues having a molecular weight of approximately
3600. A cysteine disulfide bridge at the 1-7
position of the amino terminal end of the peptide is essential
for biological activity; however, the entire amino
acid sequence is required for optimal activity.
Verwenden
Regulator (calcium).
Indications
Calcitonin (Miacalcin, Miacalcin Nasal Spray) is a synthetic
32–amino acid polypeptide that is identical to
salmon calcitonin. Salmon calcitonin is more potent
than human calcitonin because of its higher affinity for
the human calcitonin receptor and its slower metabolic
clearance. Administration is by subcutaneous or intramuscular
injection or by nasal spray. The absorption of
the nasal form is slower than that of the parenteral
routes.
Biosynthese
The regulation of calcitonin synthesis and release from
the parafollicular C cells of the thyroid gland is calcium
dependent. Rising serum calcium is the principal
stimulus responsible for calcitonin synthesis and release.
Other hormones, such as glucagon, gastrin, and
serotonin, also stimulate calcitonin release. Calcitonin
has been isolated in tissues other than the parafollicular
C cells (parathyroid, pancreas, thymus, adrenal),
but it is not known whether this material is biologically
active.
Secretagogues, such as gastrin and pancreozymin,
may contribute significantly to the regulation of endogenous
calcitonin. In fact, it has been postulated that
gastrin-induced calcitonin release following meals may
help regulate the postprandial calcium deposition in
bone.
A calcitonin precursor has been identified within the
thyroid parafollicular C cells. It is thought to function in
a manner analogous to that of proPTH to facilitate intracellular
transport and secretion of the hormone. The
metabolic degradation of calcitonin appears to occur in
both the liver and kidney.
Although blood calcitonin levels are normally low,
excessive levels have been found in association with
medullary carcinoma of the thyroid and more rarely
carcinoid tumors of the bronchus and stomach. Serum
calcitonin levels are used to screen and monitor patients
who have or are suspected of having medullary carcinoma
of the thyroid.
Biologische Funktion
In addition to its antiresorptive action via suppression of osteoclast activity, calcitonin-salmon exhibits a potent
analgesic effect and has provided considerable relief to those patients suffering from the pain associated with
Paget's disease and osteoporosis. This analgesic effect is a result of calcitonin-stimulated endogenous opioid
release. The potency of this analgesic effect has been demonstrated to be 30- to 50-fold that of morphine in
selected patients. Calcitonin is preferred over estrogen and the bisphosphonates when treatment of both
osteoporosis and related bone pain is warranted.
Acquired resistance
Resistance to calcitonin-salmon can result from the development of neutralizing antibodies.
Allgemeine Beschreibung
Calcitonin (thyrocalcitonin) is a 32-amino-acid polypeptidehormone secreted by parafollicular cells of the thyroidglands in response to hypocalcemia. The entire 32-residuepeptide appears to be required for activity, because smallerfragments are totally inactive. Common structural featuresof calcitonin isolated from different species are a COOHterminalprolinamide, a disulfide bond between residues 1and 7 at the NH
2 terminus, and a chain length of 32 residues.Calcitonin inhibits calcium resorption from bone, causinghypocalcemia, with parallel changes in plasma phosphateconcentration. In general, calcitonin negates the osteolyticeffects of parathyroid hormone.
The potential therapeutic uses of calcitonin are in thetreatment of hyperparathyroidism, osteoporosis and otherbone disorders, hypercalcemia of malignancy, and idiopathichypercalcemia.
Mechanism of action
Calcitonin interacts with specific plasma membrane receptors
within target organs to initiate biological effects.
This interaction has been directly linked to the
generation of cAMP via adenylyl cyclase activation.
Pharmakokinetik
Calcitonin-salmon differs structurally from human calcitonin at 16 of 32
amino acids. The
pharmacological activity of these calcitonins is the same, but calcitonin-salmon is approximately 50-fold more
potent on a weight basis than human calcitonin with a longer duration of action. The duration of action for
calcitonin salmon is 8 to 24 hours following intramuscular (IM) or subcutaneous (SC) administration and 0.5 to
12.0 hours following IV administration. The parenteral dose required for the treatment of osteoporosis is 100
IU/day. Initially only available by IM or SC injection, the peptide hormone calcitonin-salmon is available as
a nasal spray (Miacalcin) and as a rectal suppository. A recombinant DNA form of calcitonin salmon was
approved by the U.S. FDA in 2005 and is available as a nasal spray. The bioavailability of calcitonin-salmon
nasal spray shows great variability (range, 0.3–30.6% of an IM dose). It is absorbed rapidly from the nasal
mucosa, with peak plasma concentrations appearing 30 to 40 minutes after nasal administration, compared with
16 to 25 minutes following parental dosing. Calcitonin-salmon is readily metabolized in the kidney, with an
elimination half-life calculated at 43 minutes. As a result, the intranasal dose required is 200 IU/day. Once
the Miacalcin nasal pump has been activated, the bottle may be kept at room temperature until the medication
is finished (2 weeks)
Clinical Use
Calcitonin therapy requires the concomitant oral administration of elemental calcium (500 mg/day). Clinical
studies have shown that the combination of intranasal calcitonin salmon (200 IU/day), oral calcium
supplementation (>1,000 mg/day of elemental calcium), and vitamin D (400 IU/day) has decreased the rate of
new fractures by more than 75% and has improved vertebral BMD by as much as 3% annually. Calcitonin
prevents the abnormal bone turnover characteristic of Paget's disease of the bone and has antiresorptive
activity. In the presence of calcitonin, the osteoclast brush borders disappear, and the osteoclasts move away
from the bone surface undergoing remodeling. Side effects are significantly more pronounced when
calcitonin-salmon is administered by injection and can include nausea, vomiting, anorexia, and flushing.
Because calcitonin-salmon is protein in nature, the possibility of a systemic allergic reaction should be
considered,and appropriate measures for treatment of hypersensitivity reaction should be readily available. Although
calcitonin-salmon does not cross the placenta, it may pass into breast milk. Calcitonin-salmon is a possible
alternative to ERT; however, only limited evidence suggests that it has efficacy in women who already have
fractures.
Calcitonin Upstream-Materialien And Downstream Produkte
Upstream-Materialien
Downstream Produkte
