Module #3: Adrenal Cortex and Reproductive Hormones Flashcards
What is the role of the Adrenal Gland in the endocrine system?
Response to stress
Maintain water/salt equilibrium
Maintain BP
Sympathetic function = “extension of ANS”
What are the 2 regions of the adrenal gland?
Medulla
Cortex
What does the adrenal medulla do?
Release catecholamines –> epinephrine and norepinephrine
What does the adrenal cortex do?
Release aldosterone, cortisol, and dehydroepiandrosterone (DHEA)
What are the 3 layers of the adrenal cortex?
Zona glomerulosa = outer
Zona fasiculata = middle
Zona reticularis = inner
What does the zone glomerulosa do?
produce/secrete mineralcorticoids (ie aldosterone)
What does the zona fasiculata/zona reticularis do?
produce/secrete glucocorticoids (cortisol) and adrenal androgen (DHEA)
What is the first step of hormone synthesis in the adrenal cortex?
cholesterol –> pregnenolone
What is the enzyme that converts cholesterol to pregnenolone?
desmolase
What is the stimulus of the conversion of cholesterol to pregnenolone?
ACTH from anterior pituitary
What happens after cholesterol is converted to pregnenolone?
Pregnenolone can follow 3 pathways to form aldosterone, cortisol, or DHEA
will go to a different region to be converted to the different hormones (each region has specific enzymes for one of the pathways)
Which enzymes do the zona glomerulus (outer layer) contain?
enzymes to convert pregnenolone –> aldosterone
Which enzymes do the zona fasiculata (middle)/zona reticularis (inner) contain?
enzymes that will convert pregnenolone –> cortisol OR DHEA
What happens if there are deficiencies in the adrenal cortex enzymes?
Siginifcant adrenal pathology
How are adrenal cortex hormone production regulated?
Syntehsized @ rate of demand
NOT stored!
How do adrenal hormone levels fluctuate?
Follow Circadian Rhythm Pattern
What are the adrenal hormone stimulus signaling steps (start w/ hypothalamus)?
Hypothalamus releases CRH
CRH stimulates anterior pituitary to release ACTH
ACTH stimulates desmolase activity (cholesterol –> pregnenolone)
What is aldosterone influenced by?
Angiotensin II
ECF (extracellular fluid) K+ levels
What inhibits adrenal cortex hormone production?
Increased levels of cortisol inhibits release of ACTH and CRH = negative feed back loop
Where are glucocorticoids (cortisol) produced?
Zona Fasiculata
Zona Reticularis
What stimulates cortisol secretion?
ACTH from anterior pituitary
Normal Circadian Rhythm
Stress
What is the normal circadian rhythm of cortisol release?
Released between midnight and 8 am –> peak just before awakening
How does stress stimulate the release of cortisol?
Stimulates the release of ACTH
Alter normal circadian rhythm
What inhibits cortisol secretion?
Elevated levels of cortisol inhibits ACTH and CRH
What is the function of cortisol?
Acts as response to normal human stress:
Catabolic to produce/mobilize/store glucose
Maintains fluid volume
Modulates the immune system (anti-inflammatory response)
What are the target tissues of cortisol?
Bone
Adipose (fat) cells
Muscle
Tendon/Ligament/Connective Tissue
Immune System
CNS
Metabolism
Others
What is the action of cortisol on bones?
Stimulate osteoclasts/Ca2+ resorption –> decrease bone density
What is the action of cortisol on adipose cells?
Stimulate lypolysis –> mobilize FFA and glycerol for fuel and production of “new” glucose
Synergistic w/ glucagon, GH, catecholamines
What are the adverse results of cortisol stimulating lypolysis?
FFA are redistributed –> central obesity
Also leads to poor lipid profile
What is the action of cortisol on muscle?
Stimulates proteolysis –> mobilize amino acids for fuel and production of “new” glucose
What is the adverse result of cortisol on muscle?
Muscle wasting/weakness
Loss of lean body mass
What is the action of cortisol on tendon/ligaments/ connective tissue?
catabolic effect –> inhibits fibroblasts/collagen production
What is the adverse result of cortisol on tendon/ligaments/ connective tissue?
Ligament/Tendon failure
What is the beneficial action of cortisol on the immune system?
Anti-inflammatory –> decrease PGs, histamine, bradykinin, serotonin
What is the adverse action of cortisol on the immune system?
Poor wound healing/immune defenses –> impair T-lymphocytes, eosinophils, basophils, ILs, cell mediated immune response, antibody response, etc
What type of cortisol therapy is considered ok?
5 day taper
problem when its longer or high dose
What is the action of cortisol on the CNS?
Alters perception/mood
Negative feedback to hypothalamus (CRH)/anterior pituitary (ACTH)
What is the action of cortisol on metabolism?
Alters intermediary metabolism to produce, mobilize, store glucose
Liver = gluconeogenesis/glycogenesis
Optimizes/enhacnes effect of glucagon (lipolytic, impair glucose uptake) and catecholamines
Why does cortisol alter intermediary metabolism to produce/mobilze/store glucose?
Trying to save glucose for CNS survival –> stress response
What does gluconeogenesis do?
Uses FFA, glycerol and amino acis to form “new” glucose”
What is glycogenesis?
Glucose is stored as glycogen
What are the other effects of cortisol in the body?
Vasoconstriction/bronchodilation –> optimizes/enhances effect of caetcholamines
Fetal lungs –> surfactant production and lung development
Enhances bodes ability to tolerate stress –> cold, heat, trauma
Where are mineralcorticoids (aldosterone) produced?
Zona glomerulosa (outer)
What is the function of aldosterone?
Increase blood volume and BP by regulating renal sodium resorption = primary
Decrease plasma potassium
Increase plasma pH –> alkaline
How does aldosterone regulate renal sodium resorption?
Increases Na+ resorption in distal nephrone
What is the consequence of increasing Na+ resorption?
Increase H2O absorption (gradient follows Na+)
Facilitates K+ excretion –> decreases plasma K+
Facilitates H+ excretion –> increase plasma pH (more alkaline) and decreases urine pH (more acidic)
Describe the role that aldosterone has been suggested to play in vasoconstriction
Research suggests aldosterone is produce/secreted by non-Adrenal tissue and have paracrine effect –> aldosterone’s peripheral release contributes to vasoconstriction of blood vessels
What stimulates the release of aldosterone?
ACTH (not as influential as angiotensin II/K+ levels)
Angiotensin II
Hyperkalemia
Which system is angiotensin II involve in?
Renin-angiotensin system
What does the Renin-Angiontensin system do?
Slow hormonal system of BP regulation
Sensory cells in the kidneys monitor perfusion pressure and Na+ content of blood
What stimulates the release of renin from the kidney?
Decreased blood volume
Decreased Na+ concentration
Which cells release renin in the kidney?
Juxtaglomerular cells
What does renin do?
Trigger cascade that eventually produces angiotensin II
Where does the conversion of angiotensin to angiotensin II happen?
Blood stream
What is the enzyme that catalyzes the conversion of angiotensin to angiotensin II and where is it produced?
ACE = angiotensin- converting enzyme
produced in lungs
Clinically, what do ACE inhibitors do?
block the conversion of angiotensin –> angiotensin II –> lower BP
What does angiotensin II do?
Stimulate the production/secretion of aldosterone
What does hyperkalemia do?
Stimulates release of aldosterone from adrenal cortex
Does the K+ mechanism occur independently or dependently from the renin system?
Independently
What inhibits aldosterone secretion?
Hypernatremia = increased Na+ d/t overproduction or loss of H2O
ANP = atrial natriuretic peptide
Elevated ACTH levels (negative feedback)
Where does ANP come from?
Released in atria in response to increased BP
What does ANP do?
Inhibits renin release
Increases excretion of Na+/H2O –> opposite of aldosterone
Relaxes smooth muscles of smooth muscle vascular system –> dilation decreases TPR
What are the adrenal androgens?
DHEA = dihydroepiandrosterone
Androstenedione
Where are the adrenal androgens produced?
Zona Fasiculata (middle)
Zona Reticularis (inner)
What are androgens?
Sex hormones associated w/ the development/maintenance of male sexual characteristics –> deep voice, hair, baldness, etc
Are androgens only important in males?
No, also critical for females
What do androgens do in females?
Maintain muscle mass
Maintain bone density
Sexual desire
Sense of well being
Estrogen production
What happens when females have low androgen levels?
Low Libido
Muscle/bone mass loss
Fatigue
In males where are androgens produced?
Testes = testosterone
Adrenal cortex = DHEA/Androstenedione (later converted to testosterone)
In females where are androgens produced?
Ovaries = testosterone
Adrenal cortex = DHEA/Androstenedione (later converted to testosterone)
In females what happens to the majority of testosterone?
Converted to estrogen
Which adrenal gland androgen is produced in greater quantity?
DHEA