Endocrine System Flashcards
Upregulation
increase in number of receptors on/within a cell, allows more hormone molecules to bind receptors on target tissues
occurs when hormone levels are low
How long it takes for hormone regulation to occur in response…
hours to days
Downregulation
decrease in number of receptors on/within a cell
occurs when hormone levels are high
Negative feedback mechanisms
Maintains homeostasis
Endocrine tissue increases secretion of hormone in response to stimulus
Hormone circulates in blood to produce effects on target tissue
Hormone binds receptors on endocrine tissue which decrease secretion of hormone
How Hormones are regulated by the hypothalamic pituitary axis (negative feedback system - hormonal)
Hypothalamus secretes hormone A into pituitary portal
Hormone A stimulates cells in pituitary gland to secrete hormone B into circulation
B-C etc.
Example of Humoral Stimuli (negative feedback)
Pancreas secretes insulin and glucagon in response to levels of glucose in blood
Glucose levels are high = pancreas secretes insulin
Glucose levels are low = pancreas secretes glucagon
Example of Neural Stimuli (negative feedback)
Adrenal medulla secretes epinephrine into blood
Adrenal medulla is stimulated to secrete epinephrine by the SNS during times of stress or activity
Communication (hormone release cascade)
Hypothalamus –> pituitary gland –> endocrine gland –> tissues
Lobes of pituitary gland
Anterior
Posterior
Anterior pituitary gland hormones that are secreted
Growth hormone
Prolactin
Growth hormones
Posterior pituitary gland hormones that are secreted
Antidiuretic hormone (water balance) Oxytocin (promotes myometrial contraction during labor and delivery)
Growth hormone
promotes growth and development of bones, cartilage, muscles, glands
breaks down adipose tissue for energy
carried out by insulin-like growth factors
GH disorders
related to undersecretion and oversecretion
GH disorders - undersecretion
Dwarfism (during childhood)
- GH replacement therapy is tx
In adulthood
- signs include reduced muscle mass, increased adipose tissue, insulin resistance etc.
Abuse
- used by athletes to increase muscle mass and reduce body fat
GH drug for undersecretion
Somatropin
GH disorders - oversecretion
Childhood
- gigantism (tx with surgery)
Adulthood
- acromegaly (enlarged facial bones) - GH receptor antagonists
Deficiency pf ADH causes…
diabetes insipidus
- large volumes of dilute urine
- extreme thirst
Excess ADH secretion causes…
Syndrome of inappropriate ADH (SIADH)
- fluid retention, concentrated urine, low serum osmolality, sodium loss in urine
Diabetes Insipidus - signs
Thirst
Dilute urine
Dry skin, poor skin turgor
confusion
What side effect might you see if a high dose of vasopressin is given and why?
HTN (vasopressin is a potent vasocontrictor)
Angina (risk for MI)
Increased risk for myocardial infarction
Excessive fluid retention
What diagnostics would you include in your assessment while administering vasopressin?
Physical examination
Lab tests: renal function ( urine specific gravity, urine osmolarity, serum electrolytes)
Hormones that are secreted by the thyroid gland
T3 (tri-iodothyronine)
T4 (thyroxine)
T3/T4 help regulate
basal metabolic rate
- positive inotropic, chronotropic effects
- inc metabolism of nutrients
- inc body temp
- inc GI motility, appetite
- inc secretion of GH
T3/T4 negative feedback mechanism
hypothalamus secretes TRH into pituitary portal vein (when T3/T4 is low)
TRH stimulate anterior pituitary to secrete TSH
TSH stimulates thyroid gland to secrete T3/T4
T3/T4 have inhibitory effect on hypothalamus and anterior pituitary
T3 and T4
produced in the thyroid gland through the iodination and coupling of amino acid tyrosine
body needs 1 mg of iodine per week
When administering levothyroxine, what symptoms may occur and why?
Increases metabolic rate
- increasing oxygen consumption, respiration, HR
Increases rate of fate, protein and carbohydrate metabolism
Adrenal Gland is composed of…
Medulla
Cortex
Adrenal Medulla Secretes
Epinephrine, NE
Adrenal cortex secretes
Aldosterone
Hydrocortisone
estrogen, testosterone
Mineralocorticoids (aldosterone)
Secreted with extracellular potassium is high
Secreted in response to angiotensin II
Conserves sodium and water during dehydration, regulates plasma volume
Glucocorticoids (hydrocortisone)
secreted in response to ACTH (ACTH secreted by anterior pituitary in response to corticotropin releasing mechanism
levels change and vary during circadian rhythms, stress and inflammation
Glucocorticoids (hydrocortisone)
increase BG levels
Increase catabolism of proteins and lipids
Suppress inflammatory response and immune responses
increase sensitivity of vascular SM - Increases HR and BP
Bronchodilation
Gonadocorticoids (mostly androgens)
control onset of puberty
primary source of endogenous estrogen in postmenopausal women
Ways in preventing adverse effects of corticosteroids
- Lowest dose possible
- Apply topically locally
- Alternate day dosing to minimize adrenal atrophy
Side effects of corticosteroid therapy
Suppression of immune and inflammatory response
Peptic ulcers (mucosal lining and then the gastric acids rise causing ulcers)
Osteoporosis (suppress bone formation, muscle wasting
Behavioral changes (talkative, insomnia)
Metabolic changes
Crushings Syndrome
Causing high levels of corticosteroids over long period
results of pituitary or adrenal tumors
Can be result of long-term drug therapy systemic corticosteroids
