Flashcards in Lecture #1 -- Intro Deck (71):
Tyrosine is converted into what two types of hormones
Describe the physical structure of thyroid hormones.
Critical Incorporation of 3-4 iodine atoms
Describe how thyroid hormones are generated
Modification of a Tyrosine residue in thyroglobulin
Post translationally modified to bind iodine
Proteolytically cleaved into T3 and T4
T3/4 bind to thyroxin binding globulin for transport
Catecholamines are both ______ and ________
neurohormones and neurotransmitters
Two amino acids used to generate amine hormones?
Tryptophan is the precursor of _________
Serotonin and Pineal Hormone Melatonin
Glutamic Acid is converted to _________
All steroid hormones are derived from ______
List the five types of steroid hormones and an example
Glucocorticoids - Cortisol
Mineralocortioids - Aldosterone
Androgens - Testosterone
Estrogens - Estradiol, Estrone
Progestogens - Progesterone
Where in the cell are enzymes that produce steroid hormones
Mitochondria and Smooth ER
Steroids are not water soluble. So what?
They have to be carried in the blood complexed to binding globulins
Steroids secreted in one cell may be converted to _______
active steroid in the target cell
Common prefix for the enzymes that convert steroids
Other name for 21-hydroxylase
Review the picture of steroid hormone conversion -- page 8
Should have been paying attention on that one...
CYP important from conversation from testosterone to estrogen
CYP that makes cortisol
CYP importnat for aldosterone production
What is the rate limiting step in the process of steroid hormone synthesis?
Transport of free cholesterol from cyto into mito
Performed by Steroidogenic Acute Regulatory Protein
Where does the steroidogenesis precursor cholesterol come from?
Cholesterol synthesized in the cell from acetate
Cholesterol ester stores in intracellular lipid droplets
Uptake from cholesterol-contining LDL
Which source of cholesterol is most important in chronic stimulation?
What "vitamin" is also made from cholesterol
1, 25 - dihydroxy Vitamin D3
Most abundant precursor of Eicosanoid hormones
(Polyunsaturated Fatty Acids)
How long do eicosanoids last?
They are typically active for only a few seconds before they are metabolized
Principal groups of eicosanoid hormones? (4)
Prostaglandins, Prostacyclin, Leukotrienes, and Thromboxanes
What are eicosanoids?
A large group of molecules derived from polyunsaturated fatty acids
The physiological effers of hormones deped largely on their concentrations where?
Blood and Extracellular Fluid
Three factors that determine the concentration of hormone seen by a target cell?
Rate of Production
Rate of Delivery
Rate of Degradation and Elimination
Most highly regulated aspect of endocrine control?
Rate of Production
What factor plays a major role in the efficacy of controlling circulating hormones by shutting off secretion?
Hormone half life
_____ input to hypothalamus stimulates synthesis and secretion of releasing factors
What does chronotropic control refer to?
Endogenous neuronal rhythmicity
Diurnal rhythms, Circ rhythms, sleep-wake cycle
How frequent is a circhoral rhythm?
Frequency of approx 1 hr.
How frequent is a ultradian rhythm?
Longer than an hour, less than 24
How frequent is a circadian rhythm?
Periodicity of approx 24 hours.
Circadian clock is located in the ______ nucleus
Give an example of the significance of pulsatile hormone release.
GnRH one hourly --- > Normal gonad function
Slower Frequency --> Diminished Gonadal Fxn
Faster Frequency/Continuous --> Inhibits gonadal steroid production
Give an example of substrate-hormone control
Glucose and Insulin
(High Plasme Glu triggers insulin, insulin lowers glucose levels, decreased insulin response)
What is MCR (in regard to endocrine)
Metabolic Clearance Rate
Defines the Quantitative Removal or Hormone from Plasma
Who clears most of the hormones from blood
Who does a little
Liver and Kidneys
Target tissue responsible for small fraction
99% of excreted hormone is _____ or _______
Degraded or Conjugated by Phase I and II enzyme systems
Compare the MCR of T3 and T4
T3 -- 0.75 Days
T4 -- 6.7 Days
Two types of hormone solubility?
Water and Lipid Soluble
List water soluble hormones
List lipid soluble hormones
Three most common second messenger systems for cell surface receptors
Adenylate Cyclase (ATP-->cAMP)
Guanylate Cyclase (GMP-->cGMP)
Calcium and Calmodulin (Phospholipase C-->PIP+DAG)
Four types of receptors to remember
Ligand Gated Ion Channels
Important trait of second messenger activity
Usually allows for amplification of individual signals
Give a few examples of receptors that use Adenylate cyclase
LH, FSH, TSH, hCG
Receptors for growth factors, insulin, etc. usually have _____ activity
intrinsic tyrosine kinase
Receptors for Growth Hormone, Prolactin, and other cytokines typically have _______ activity
Soluble, Intracellular kinase
Give examples of receptors with intrinsic serine/threonine kinase activity
Mullerian Inhibitory Factor
Describe the process of lipid-soluble hormone binding
Hormones diffuse through lipid bilayer
Binds receptor in cyto or nuc, conformational change
Complex binds specific DNA response element in regulatory region
Why do lipid hormones take longer to trigger a response
Requires transcription/translation to evoke physiological responses
What is homologous desensitization?
Hormonally induced negative regulation of receptors
Why is homologous desensitization important?
Protects from toxic effects of too much hormone
What is heterologous desensitization?
When exposure of the cell to one agonist reduces the responsiveness of the cell to any other agonist that acts through a different receptor
When does heterologous desensitization tend to occur?
(Whats happening, how long)
Through receptors that act on Ad. Cyclase system
Slower onset than homologous desensitization
What hormone can be deficient without causing disease?
Common causes of endocrine deficiency?
Receptor Inactivating Mutation
Examples of gland problems leading to endocrine deficiency
Infection, Infarction, Tumor, Autoimmune
Examples of genetic defects that might cause endocrine deficiency?
Gene Mutation, Protein Folding Defects, Enzymatic Defects
How does hormone excess tend to happen?
Overproduction by normal glad to secrete it
Production by non-endocrine tissue
Receptor activating mutations
Cancer of non-endocrine, allowing dediferentiation
Example of a Dynfunctional glad deficiency
Type I Diab
Give an example of a genetic defect deficiciency
Congenital Adrenal Hyperplasia
Give an example of a receptor inactivation that causes hor deficiency
Testicular Feminization Syndrome
Example of overproduction by a gland that normally secretes is
Examples of endogenous ingestion of hormones
Anabolic Steroid Abuse
Example of a receptor activating mutation?
Example of malignant transformation in endocrine disease?