Assessment of Endocrine Function Flashcards
Two-site immunometric assay
Enzyme is added to coated antibody well; more antibody is added to bind to other part of enzyme
=>Formation of compound is measure spectrophotometrically
Bioassay
Determines the circulating pool of biologically active hormone by using hormone receptors to measure enzyme concentration in place of antibodies
*Could also measure the formation of secondary messengers
Stimulation Tests
Test substance is administered; amount of hormone produced by gland is measure
- Substances could be exogenous hormones, physiological stimuli
- Used when a gland is thought to be HYPOfunctional
Suppression Tests
Assesses the functioning of the negative feedback loop; failure to suppress is indicative of HYPERfunctioning gland
Kd
Dissociation constant= 1/Ka
- Is an indicator of receptor affinity (inversely related)
- Also equivalent to the concentration of hormone required for 1/2[HR]
Conditions that affect [H]
Endogenous signals
Dysunctional glands
Conditions that affect Ka
Covalent/Allosteric Receptor Modifications
Altered pH
Antibodies to receptor
Mutations
Conditions that affect [R]
Altered rate of receptor synthesis/degradation
Compartmentalization of the receptors
Threshold
Minimum concentration of a hormone required to produce a detectable response
ED50
Sensitivity- half the concentration of hormone required to produce the maximum response
Maximum Response
the effect produced by saturating the hormone
ED50>Kd
Spare receptors present
Greatly enhances the sensitivity to the hormone
*May play a role in hormone degradation via receptor-mediated endocytosis
Maximum responsiveness decreases
Caused by: decreased # of responsive cells
increased conc. of non-competitive inhibitors
decreased # of receptors
*Cannot be overcome by increased [H]; unlike receptor sensitivity
Metabolic Clearance Rate
Rate of disappearance from plasma/Concentration of the hormone in the plasma
*Inversely related to half-life
Hormone Response
HR= Ka(H)(R)
