Cortisol binding globulin

CAT-REL, vesicular catecholamine release CB-R, cannabinoid receptor CB1-R, CB2-R, cannabinoid receptors CBD, chitin-binding domain CBG, cortisol-binding globulin CBZ-R, central benzodiazepine receptor CCK-R, cholecystokinin receptor CDC, chrysanthemum dicarboxylic acid CDK, cell division kinase, cyclin-dependent protein kinase... 

ACE-I angiotensin-converting enzyme inhibitor CBG cortisol binding globulin... 

Steroid hormones (e.g., cortisol and estrogen) are hydro-phobic and insoluble in water. These hormones circulate in plasma, reversibly bound to transport proteins (e.g., cortisol-binding globulin and sex-hormone binding globulin) with only a small fraction free or unbound available to exert physiological action.The half-life of steroid hormones is 30 to 90 minutes. Free steroid hormones, being hydrophobic, enter the cell by passive diffusion and bind with intracellular receptors either in the cytoplasm or the nucleus. ... 

Transport to tissues Cortisol is secreted into the blood stream where it is 90% bound to cortisol-binding globulin (CBG) and albumin. Active cortisol (remaining 10%) freely diffuses into cells where it exerts its actions via intracellular receptors. CBG plays an important role in regulating cortisol delivery and clearance. Dexamethasone has low affinity for CBG. It... 

In the serum, progesterone is bound to either cortisol binding globulin or albumin, with only a small fraction being freely available. The metabolic clearance rate for progesterone is 2,100 to 2,500 L/day, for which protein binding has no role. 

Ceruloplasmin (contains Cu + albumin probably more important in physiologic transport of Cu T Corticosteroid-binding globulin (trans-cortin) (binds cortisol)... 

Oral contraceptives have their most significant effect on endocrine parameters. Blood cortisol, thyroxine, protein-bound iodine, T3 uptake, and urinary free cortisol are elevated. Urinary 17,21-dihydroxy steroids, 17-ketosteroids, and estrogens are decreased. There is no effect on urinary catecholamines or VMA (Table 10) (LIO). The effect of thyroid functions tests is due to the administered hormone stimulating an increase in the production of thyroid-binding globulin which in turn binds 1-thyroxine. The lowering of free thyroxine stimulates the anterior pituitary to produce thyrotropin, which in turn stimulates the thyroid to produce more thyroxine. Since the additional thyroxine is bound to the extra protein, there is an equilibrium and the patient remains clinically euthyroid, but the protein-bound iodine and the thyroxine are elevated. 

Kanter et al. reported an increase concentration of the corticosteroid binding globulin (CBG) (Kanter et al. 2001). Most cortisol is bound to CBG, and is biologically inactive. A greater concentration of CBG is consistent with low levels of measurable free cortisol, and provides a putative explanation for how cortisol levels could be measurably low even though other aspects of HPA axis functioning do not seem hypoactive. However, the extent to which CBG levels are a contributing cause of low cortisol requires further examination. 

Thyroid hormones and most steroid hormones are associated with carrier proteins in the serum. The carrier proteins are called, appropriately, thyroxine-binding globulin, transcortin (for cortisol), and sex-steroid-binding protein. These proteins have a high affinity (Kd 10—9— 10 8 m) for their respective hormones. They buffer the concentration of free hormone and retard hormone degradation and excretion. The carrier proteins are distinguishable from the intracellular receptors for these hormones. 

Possible consequences of the loss of binding proteins (e.g., ceruloplasmin, transferrin, vitamin D-binding protein, thyroxin-binding globulin, and cortisol-binding protein) have been already mentioned. 

In determining cortisol in serum, most of the cortisol is bound to corticosteroid-binding globulin and other serum proteins. How then is cortisol released for detection [1006] (2 marks)... 

Alkaline phosphatase is one of the most suitable enzymes for electrochemical immunoassays owing to its high turnover number and broad substrate specificity. Different substrates have been used, but 4-aminophenyl phosphate is most suitable, since the reaction product, 4-aminophenol is easily oxidized without fouling of the electrode surface. Thyroxine-binding globulin, cortisol, and prostatic acid phosphatase have been detected by using alkaline phosphatase. 

Anderson KE, Rosner W, Khan MS, et al Diet-hormone interactions protein/carbohydrate ratio alters reciprocally the plasma levels of testosterone and cortisol and their respective binding globulins in man. Life Sci 40 1761-1768,1987... 

Plasma cortisol concentration is increased because of decreased metabolic clearance. The plasma concentrations of total triiodothyronine T3), thyroxine (T4), and TSH are considerably reduced, with the thyroxine concentration being most affected. This is partly due to reduced concentrations of thyroxine-binding globulin and prealbumin. 

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