Hormone Life History Flashcards
What are the three factors that determine the concentration of a hormone at target cells?
- Rate of production
- Rate of delivery
- Rate of degradation and elimination
These factors are crucial for maintaining hormone levels within physiological ranges.
What is the significance of hormone concentration in blood/extracellular fluid?
Physiologic effects of hormones depend largely on their concentration in blood/extracellular fluid
Disease can result from either too high or too low hormone concentrations.
What is the role of feedback circuits in hormone regulation?
Feedback circuits mediate the synthesis and secretion of hormones
Both positive and negative feedback mechanisms are involved.
How are lipid-soluble hormones transported in the blood?
Lipid-soluble hormones are transported bound to specific transport proteins
Examples include corticosteroid binding globulin (CBG) and thyroxine binding globulin (TBG).
What is the bioactive form of a hormone?
Free hormone is the bioactive form
Protein binding can affect the metabolism and bioactivity of circulating hormones.
What is the half-life of a hormone?
The time during which the concentration of hormone decreases to 50% of its initial volume
Hormones have characteristic rates of decay.
How does a hormone’s half-life affect its secretion?
Shutting off secretion of a hormone with a very short half-life causes circulating hormone concentration to plummet
This can lead to rapid physiological changes.
What is metabolic clearance rate (MCR)?
Removal of hormones from circulation, the volume of plasma cleared of the hormone per unit time
MCR is influenced by hormone half-life and protein binding.
What are Phase I reactions in metabolic degradation of hormones?
Phase I reactions include oxidation, reduction, hydroxylation, and decarboxylation
These reactions primarily occur in the liver.
What are Phase II reactions in metabolic degradation of hormones?
Phase II reactions include methylation, glucuronidation, and sulfation
These reactions help in making hormones more water-soluble for excretion.
What actions can hormones have once they arrive at a target cell?
- Alter plasma membrane permeability
- Stimulate synthesis of proteins or regulatory molecules
- Activate or deactivate enzyme systems
- Induce secretory activity
- Stimulate mitosis
The specific action depends on the hormone’s chemical nature.
True or False: Hormones can only act on target cells by altering membrane permeability.
False
Hormones can also stimulate protein synthesis, activate enzymes, and induce secretory activity.
Fill in the blank: The concentration of a hormone as seen by target cells is influenced by the rate of _______.
production, delivery, degradation, and elimination
All these factors work together to determine hormone levels.
What is the primary organ responsible for metabolizing hormones?
Liver
The kidneys also play a role in excretion of hormone metabolites.
What type of hormones circulate in the blood either free or bound?
Both water-soluble and lipid-soluble hormones
Water-soluble hormones have no specific transport mechanism, while lipid-soluble hormones rely on transport proteins.
What happens to free hormones in circulation?
Free hormones equilibrate with the forms bound to either receptors or plasma carrier proteins
This equilibrium affects their bioactivity.
