Plasma calcium level

Dose of elemental calcium should not exceed 1.5-2 g/d and plasma calcium levels should not exceed 9.5 mg/dL (to avoid coronary artery calcification resulting from excess calcium)... 

The release of calcitonin from the thyroid is regulated by plasma calcium levels through negative feedback. An increase in the level of calcium in the... 

The final mechanism of action of PTH involves the activation of vitamin D3 through the stimulation of la-hydroxylase in the kidney. In the gastrointestinal tract, vitamin D3 is essential for the absorption of calcium. Enhanced absorption of calcium from dietary sources serves to further increase the concentration of calcium in the blood. Many foods, in particular, dairy products, which are rich in calcium, are fortified with vitamin D. The release of PTH from the parathyroid glands is regulated by plasma calcium levels through negative feedback. A decrease in the level of calcium in the blood stimulates the secretion of PTH and an increase in the calcium level in the blood inhibits it. 

Calcitonin a peptide hormone secreted by the thyroid gland that lowers plasma calcium levels by increasing the deposition of bone. 

Hypocalcemia - To correct plasma calcium levels (eg, neonatal tetany and tetany due to parathyroid deficiency, vitamin D deficiency, alkalosis) prevention of hypocalcemia during exchange transfusions conditions associated with intestinal malabsorption. 

Hypercalcemia is a common clinical condition that can accompany a variety of other medical conditions, such as sarcoidosis, vitamin D toxicity, hyperparathyroidism, and malignancy. When calcium levels are exceptionally high, adjunctive measures for the control of plasma calcium levels are necessary, as this is a medical emergency. Various modalities in combination are used to treat this condition intravenous hydration with normal saline and the use of loop diuretics (e.g., furosemide) to induce calcium diuresis are the most important supportive measures. 

Nasal absorption. Sucrose ester of coconut fatty acid in aqueous ethanol solution (sucrose cocoate SL-40) administered intrana-sally to anesthetized male Sprague-Dawley rats at a dose of 0.5% sucrose cocoate with insulin, produced a rapid and significant increase in plasma insulin level with a concomitant decrease in blood glucose levels. Administration of a dose of 0.5% sucrose cocoate with calcitonin produced a rapid increase in plasma calcitonin levels and a concomitant decrease in plasma calcium levels . 

Plasma calcium level is precisely regulated by three hormones e.g. parathormone, calcitonin and calciferol (which is a active form of vitamin D). They control its absorption, exchange with bone and excretion. 

Calcium is present in three forms e.g., as free calcium ion, bound to plasma protein albumin and in diffusable complexes. The endocrine system, through parathyroid hormone and calcitonin, helps in keeping the concentration of ionized plasma calcium in normal level. Decrease in plasma levels of ionized calcium leads to increased parathyroid hormone secretion. Parathyroid hormone tends to increase plasma calcium level by increasing bone resorption, increasing intestinal absorption and increasing reabsorption of calcium in kidney. Vitamin D acts by stimulating... 

Rapid intravenous injection of the sodium salt of EDTA depletes blood calcium levels and produces hypocalcaemic tetany, but, carefully administered, this agent can be used to treat hypercalcaemia and to overcome digitalis-induced arrhythmia by adjusting the Ca2+/K+ balance61). The ready availability of calcium ion from extracirculatory stores enables slow (drip) infusion of sodium EDTA without untoward effects. Continued over several days, calcium is mobilised from bone and calcium EDTA is excreted in the urine but plasma calcium levels are not greatly affected62). Although it has been little explored, drip infusion of sodium EDTA,... 

To improve the absorption of peptides and proteins, the employment of different enzymatic inhibitors has been suggested. For example, some authors have demonstrated the usefulness of inhibitors of both exo- and endopeptidases to promote calcitonin absorption across rat vaginal mucosa [93]. A direct relationship was found between the effect of peptidase inhibitors of in vitro degradation constant of calcitonin in vaginal mucosa homogenates and in vivo promotion of drug absorption, indicated by the decrease in plasma calcium levels after calcitonin administration in rats. The peptidase inhibitors tested were pepstatin, bestatin, and leupeptin. 

The primary factor regulating PTH release is the level of calcium in the bloodstream.42 Parathyroid gland cells appear to act as calcium sensors that monitor circulating calcium levels. As circulating calcium levels fall below a certain point, PTH secretion is increased. Conversely, elevated plasma calcium titers inhibit PTH secretion. The ability of PTH to control plasma calcium levels and regulate bone mineral metabolism is discussed in more detail in Chapter 31... 

PTH is a polypeptide hormone that is synthesized within the cells of the parathyroid glands. The primary factor controlling the release of PTH is the amount of calcium in the bloodstream.36 A calciumsensing receptor is located on the outer surface of the parathyroid cell membrane, and this receptor monitors plasma calcium levels.11,88 A decrease in plasma calcium activates this receptor and causes increased release of PTH. As blood calcium levels increase, the receptor is inhibited, and PTH release is reduced. 

Consequently, bone is a rather dynamic tissue that is constantly undergoing changes in mineral content and internal structure. The balance between bone resorption and formation is controlled by the complex interaction of local and systemic factors. In particular, several hormones regulate bone formation and help maintain adequate plasma calcium levels. The primary hormones involved in regulating bone mineral homeostasis are described below. 

Calcitonin Human calcitonin (Cibacalcin) Salmon calcitonin (Calcimar, Miacalcin) Mimic the effects of endogenous calcitonin and increase bone formation in conditions such as Paget disease and osteoporosis also used to lower plasma calcium levels in hypercalcemic emergencies... 

Recent studies have shown that the binding of ligands to GPIIb/llla also activates a number of cellular processes important for platelet stimulation (50) including the synthesis of 3-phosphorylated phosphatidylinositols, the release of arachidonic acid, and the increase in plasma calcium levels. Stimulation of these processes allows for bidirectional signaling between the intracellular and extracellular compartments. 

For an intended drug uptake in the stomach, the only proteolytic enzyme which has to be inhibited is pepsin. It has been demonstrated that the polymeric pepsin-inhibitor conjugate chitosan-pepstatin was capable to efficiently protect the peptide drug calcitonin in the presence of pepsin. These results have been additionally confirmed in vivo. The administration of minitablets comprising of a mixture of calcitonin, chitosan, and chitosan-pepstatin to rats led to a reduction of the plasma calcium level, whereas no effect was observed when... 

Fig. 4.5 Decrease in plasma calcium level after oral administration of calcitonin in tablets based on -x- chitosan, -o- chitosan-pepstatin, and chitosan-pepstatin/ chitosan-TBA each point represents the mean SD of at least three experiments. Figure adapted from Guggi et al. (2003)...

Fig. 8.4 Decrease in plasma calcium level as a biological response for the salmon calcitonin bioavailability in fasted rats after oral administration of chitosan minitablets ( ), chitosan/ chitosan-pepsin inhibitor conjugate minitablets ( ) and thiolated chitosan/chitosan-pepsin inhibitor conjugate minitablets (A), all containing 50 pg of the peptide drug. Indicated values are the mean results from five rats S.D. (Guggi et al. 2003)...

Fig. 10.13 Profiles of plasma calcium levels after intragastric administration of submicronsized liposomes, ssLip, and ssCS-Lip containing calcitonin (taken from Takeuchi et al. 2005a) The measured mean particle sizes of ssLip and ssCS-Lip were 196.4 and 473.4 nm, respectively. The formulation of liposomes was DSPC DCP cholesterol = 8 2 1. The concentration of chitosan for coating was 0.3%. p<0.05, p<0.01, p<0.001 significantly different from the level for calcitonin solution tp<0.05, t1p<0.0l significantly different from the level for ssLip (n=3 in each case).

CALCIUM IRON-ORAL L iron levels when iron is given orally. Possibly l calcium levels i absorption. These two minerals compete for absorption Separate doses as much as possible monitor FBC closely. Monitor plasma calcium levels... 

When plasma calcium level falls the major sites of action of calcitriol and PTH are bone where they stimulate bone resorption and the kidneys where they inhibit calcium excretion by stimulating reabsorption by the distal tubules. 

A vitamin-deficient diet can result in lowered levels of plasma calcium however, the use of high-calcium diets during vitamin deficiency can result in the maintenance of normal plasma calcium levels. The requirement for the vitamin may be overridden, providing that the diet contains high levels of calcium. The physiologically important form of vitamin D, 1,25 dihydroxyvitamin Dj, is a hormone. Another hormone, parathyroid hormone (I TH), is used in the control of vitamin D metabolism and calcium levels, as detailed in the following sechon. 

The role of vitamin Din the regulation of plasma calcium levels involves complex mechanisms. Our discussion of these mechanisms begins with the concrete and vivid example of "milk fever," This example might be used as a reference point while reading through the studies on chicks, rats, and humans. 

Milk fever is a problem on the dairy farm. The disease occurs in cows whose plasma calcium levels drop below 5.0 mg /100 ml. Milk fever often results in coma and death. The disease presents when a cow has been fed a diet high in calcium prior to calving and lactation. ("Calving" means giving birth to a calf.) Alfalfa is an example of a high-caJeium food- The mother cow starts to produce milk at the lime of calving. The milk production places a sudden drain on the calcium present in the cow s plasma. This calcium must originate either from the diet or from the bones of the cow. Animals are able to dissolve or "mobilize" calcium from their own bones in times of need to maintain plasma calcium levels. 

FtCURE 9,54 Plasma calcium levels of rats fed (A) vitamin-deficient diets and (B) ejta-min-sufficient diets. (Redrawn with pGimission from Brommage and EteLuca, 1985.)... 

Although it might seem reasonable to treat osteoporosis with vitamin D, it must be realized that the primary funebon of vitamin D is to maintain plasma calcium levels, not to promote bone formation. An end-effect of vitamin D supplementa-hon is an increase in bone resorpbon and increased excretion of calcium in the urine. Calcium supplements should not be used indiscriminately Two types of persons should not receive calcium supplements persons with hypercalcemia and persons with kidney stones or a family history of kidney stones. These two issues are discussed in the following pages. 

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