Introduction to Endocrinology Flashcards
What are essentials of the endocrine system
glands that secrete hormones through blood that have actions on organs
Characteristics of hormones
Rates and rhythyms of secretion
- circadian/diurnal
- pulsatile
- cyclic
- patterns that are determined by substrate
operate in feedback systems to maintain homeostasis
affect cells with appropriate receptor
excreted by kidney or metabolized by liver and then excreted from kidney
Endocrine components
Hypothalamus Pituitary gland Pineal gland Thyroid gland Parathyroid gland Adrenal Pancreas Ovaries Testies
Hormone types (characterized by)
Function
- autocrine = act on itself
- paracrine = act in a region
- endocrine = communicate over a distance
Structure
- Proteins/polypeptides
- Steroids
- Amine
What is an example of a continuous pattern
Little variation in serum level
- Thyroxine (T4)
What is an example of a intermittent pattern
Circadian - Gonadotropins - Cortisol Cyclic - Estrogen - Progesterone - LH -FSH
What is an example of a fluctuating pattern
Responsive to external stimuli or changes homeostasis
- Insulin
- Glucagon
- Aldosterone
- ADH
- PTH
Protein/Polypeptide Hormone Summary
Def: MOST hormones in the body!
Char: - Insulin, growth hormone, prolactin - Water soluble - circulate in free (unbound forms) - short- half life • Insulin – 3-5 minutes prior to catabolism
MOA:
- Synthesized in the endoplasmic reticulum of originator
cell
- Travels to the Golgi apparatus
- Repackaged into vesicles
- Attach to receptor on target cell surface
- Initiating a secondary messenger system
Steroid Hormone Summary
Def: Lipids - derived from cholesterol
Char:
• Primarily circulate bound to carrier or binding proteins
- Free hormone signal target cells
• Travels to receptor inside the target cell – primary
messenger
- Located cytoplasm or nucleus
- Affects transcription and translation of protein
• Ex. Adrenal androgens (progesterone and estrogen) and
cortisol
• Free cortisol rises in liver disease
Amine Hormone Summary
Def: Derivatives of single amino acid (tyrosine)
Char:
• Fast and slow acting
Types: Thyroid - Slow acting with long half life - Steady state - Acts at nuclear level - Examples: * Thyroxine (T4) * Triiodothyronine (T3)
Catacholamines
- Fast acting with short half life
- bind to cell surface
- emergent response
- Examples:
- Epinephrine
- Norepinephrine
- Dopamine
What determines a hormone effect
- Number of hormone molecules
- Number of hormone receptors
- Binding affinity between hormone and receptor
What is up-regulation
Low concentrations of hormone increase the number of
receptors per target cell
• Example:
- pregnancy the cells of the uterus develop more receptors for oxytocin
- ultimately lead to more uterine muscle contraction during labor
What is down-regulation
High concentrations of hormone decrease the number of
receptors per target cell
• Example:
- increase of blood glucose causes the pancreas to increase the production of insulin
- the liver decreases the number of receptors to insulin
What is Hypothalamic-pituitary axis (HPA)
Hypothalamus tells pituitary gland to release hormones that affect most endocrine systems
- Thyroid gland
- adrenal gland
- gonads
What are the cell types in the Pituitary gland
thyrotroph somatroph gonadotroph corticotroph lactotroph
