Diagnostic Salivary Cortisol EIA Kit
Product:
AM/PM Salivary Cortisol Enzyme Immunoassay
Intended Use:
Quantitative measurement of salivary Cortisol
FDA:
510(k) FDA Approved
Catalog Number:
631
Method:
Enzyme Immunoassay (EIA), Colormetric
AMR:
0.1 ng/mL – 30 ng/mL
LOD:
0.05 ng/mL
Sample Size:
25 µL
Incubation:
1hr @ Room Temperature
# of tests:
96 wells
Reading:
450nm
Storage:
2° - 8°C
Shelf Life:
16 Months
Assay Background:
In 1966, Katz and Shannon (1,2,3) using the Porter-Silber method were able to determine corticosteroid concentrations in saliva and were able to show that concentrations of corticosteroids in saliva, were related to blood concentrations. The advent of immunoassay made it possible to measure minute amounts of steroid hormones in blood. Subsequent modification of those assays allowed their measurement in saliva as well. These early assays, however, lacked validity due to matrix differences between serum and saliva, poor sensitivity and cumbersome extraction methods. Recently, several papers have been published on the determination of salivary Cortisol under varying physiological conditions using more specific and sensitive EIA and ELISA methods (18,20).
Cortisol (hydrocortisone, compound F) is the principle glucocorticoid secreted by the adrenal cortex. Adrenal secretion of cortisol is modulated by a complex negative feedback mechanism involving the central nervous system, hypothalamus, pituitary and adrenals. ACTH released from the pituitary augment’s adrenal secretion of cortisol. In turn, increased levels of cortisol suppress pituitary secretion of ACTH while falling levels of cortisol are associated with rising levels of ACTH. Normally there is diurnal variation of cortisol with highest values measurable in the morning samples and lowest values obtained in the late afternoon. Cortisol levels rise independently of this circadian rhythm in response to stress or depression. Increased cortisol production is associated with Cushing’s Syndrome and adrenal tumors while decreased production of cortisol is associated with adrenal insufficiency (Addison’s disease) and adrenocorticotropic hormone (ACTH) deficiency (21, 22, 23, 24).
In blood 90% of the circulating cortisol is firmly bound to cortisol binding globulin (CBG), 7% is weakly bound to albumin and only 1-3% is free or unbound. In saliva the majority of cortisol occurs in the free or unbound form and enters the saliva via intracellular mechanisms (25). Numerous studies consistently report a high correlation between serum and saliva cortisol indicating that salivary cortisol levels clinically confirm levels of cortisol in serum (26, 27, 28).
Assay Principle: