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
What is the hypothalamic-pituitary portal circulation
Allows hormones from hypothalamus to reach anterior pituitary:
• Rapidly
• High concentrations
• Preserves pulsatile output
What hormones are released from the posterior lobe of the pituitary gland
Vasopressin
Oxytocin
What are stimulation/provocation tests used for
assess hypoactive hormone function
What are suppression tests used for
assess hyperactive hormone function
What is thyroid-stimulating hormone
glycoprotein hormone synthesized in thyrotroph cells in anterior pituitary
- cause secretion of T3 and T4
What do the thyroids do
synthesize
- T3
- T4
What do adrenals do
synthesize - catacholamines glucocorticoids mineralcorticoids androgens estrogens
adrenocorticotropic hormone tests
plasma cortisol
plasma ACTH
ACTH provacation/stimulation test
dexamethasone suppression test
What are conditions associated with adrenals
Hypofunction • Addison’s Disease • Low ACTH Hyperfunction • Cushing’s Disease • Androgens • Aldosterone • Catacholamines • pheochromocytoma
What does the pancreas do
Endocrine
- insulin
- glucagon
alpha cells = glucagon
beta cells = insulin
delta cells = somatostatin
What does parathyroid do
Maintains tight control of serum calcium levels and in turn phosphorus ion
What does Pineal gland do
Monitors circadian rhythm and sleep/wake cycle
Produces Melatonin
Melatonin induces drowsiness and core body temperature
What are common endocrine disorders
- Obesity
- Over-weight
- T2DM
- Thyroid Disease
- Hyperlipidemia
- Erectile dysfunction
- Infertility
- Gynecomastia
- Osteoporosis
- PCOS
- Hirsutism
Less common • Parathyroid Disorders • Adrenal Disorders • Hyperprolactinemia • Growth pattern disturbances • Puberty disorders
What are common symptoms endocrine dysfunction
Bodysize/shape
– Short, tall, weight loss / gain
Metaboliceffects
– Fatigue, weakness, appetite / thirst, urinary changes
Localeffects
– Swelling, HA, visual changes, exophthalmos
Reproduction/sexual
– Libido, impotence, fertility, puberty, breast changes
Skin
– Hair, pigment, moisture, sweating
