Endocrine: Module III Flashcards
What are the 4 important roles of the adrenal gland in the endocrine system?
- Response to stress
- Maintain water/salt equilibrium
- Maintain BP
- Sympathetic function
What are the 2 regions of the adrenal gland?
Cortex and Medulla
What does the cortex release?
Aldosterone
Cortisol
Dehydroepiandrosterone (DHEA)
What does the medulla release?
Catecholamines (epi, NE)
What are the 3 layers of the Adrenal Cortex?
- Zona glomerulosa (outer)
- Zona fasiculata (middle)
- Zona Reticularis (inner)
What does the zona glomerulosa layer of the adrenal cortex secrete?
Mineralcorticoid (aldosterone)
What does the zona fasiculata and zona reticularis layers of the adrenal cortex secrete?
Glucocorticoid (cortisol)
Adrenal androgens (DHEA/Androstenedione)
Cholesterol is converted into _______ by the enzyme _____. This is stimulated by _____.
Pregnenolone
Desmolase
ACTH
Are hormones ever stored?
NO! They are synthesized at rate of demand
Hormones tend to follow ____ _____ patterns.
Circadian rhythm
Do adrenal hormones follow the positive or negative feedback system?
Negative feedback…
Inc. levels of cortisol will inhibit release of ACTH and CRH
Where are glucocorticoids (cortisol) produced?
Zona fasiculata and zona reticularis
Stimulus for cortisol secretion:
ACTH from ant. pituitary
2 Factors that influence cortisol secretion:
- Normal circadian rhythm (most released between midnight and 8am)
- Stress (stimulates release of ACTH)
Inhibition of cortisol secretion:
Elevated levels of cortisol inhibit ACTH and CRH (negative feedback)
Function of cortisol (3)
Acts as a response to human stress
- Catabolic to produce/mobilize/store glucose
- Maintains fluid volumes
- Modulates immune system (anti-inflammatory response)
Cortisol effects in the bone:
- stimulate osteoclasts/calcium resorption
2. Adverse: decrease bone density
Cortisol effects in adipose cells:
- Stimulate lypolysis
Cortisol effects in muscle cells:
Stimulate proteolysis
Adverse effect: muscle wasting/weakness
Cortisol effects in tendon/ligament/connective tissue:
Catabolic effect (inhibits fibroblasts/collagen production)
Adverse Effect: poor wound healing/immune defenses
Cortisol effects in CNS:
Alters perception andmood
Negative feedback to hypothalamus
Cortisol effects in metabolic system:
- Alters intermediary metabolism to produce, mobilize and store glucose
- In Liver: gluconeogenesis, glycogenesis
- Optimizes/enhances effect of glucagon and catecholamines
What is cortisol needed for in terms of fetal lungs?
Necessary for surfactant production and lung development
What is the primary function of mineralcorticoids (aldosterone)
Increase blood vol/BP by regulating renal sodium resorption
–> also causes dec. plasma potassium, inc. plasma pH
2 Actions of Aldosterone?
- Increase sodium resorption in distal nephron
2. Vasoconstriction
What does sodium resorption by aldosterone lead to?
- Increased water absorption
- Facilitates potassium excretion
- Facilitates hydrogen excretion
- -> inc. plasma pH
What are the 3 stimuli for aldosterone secretion?
- ACTH
- Angiotensin II
- Hyperkalemia
Describe how angiotensin II stimulates the release of aldosterone
Dec. blood volume/sodium concentration stimulates release of renin
Renin triggers cascade of conversion to produce angiotensin II in the bloodstream
ACE (angiotensin-converting enzyme) is the catalyst for this
Angiotensin II stimulates the _____ aldosterone while hyperkalemia stimulates the _____ of aldosterone.
production/secretion
Release
3 Factors that inhibit aldosterone secretion
- Hypernatremia
- ANP (antrial natriuretic peptide)
- Elevated ACTH levels
Hyperkalemia
Elevated plasma potassium (K)
Hypernatremia
Elevated sodium in bloodstream
What are the “adrenal androgens”
DHEA and androstenedione
While adrenal androgens are important in development/maintenance of male sexual characteristics, they are also critical in females for : (4)
- Maintaining muscle mass
- Maintaining bone density
- Sexual desire
- Sense of well being
Where are androgens produced in males? In females?
Males: testes
**Adrenal gland also produces it but not in significant amts
Females: ovaries
Explain the significance of the adrenal cortex’s production of androgens in males v. females
More significant in females…about 50% is produced there and plays a role in axillary and pubic hair growth
What is the most abundant circulating hormone in the body?
DHEA
DHEA is a “____ androgen”
weak.
Poor binding affinity to androgen receptors in the body
Excessive adrenal androgens cause (pre-puberty): (males and females)
Males: isosexual precocious puberty
Females: heterosexual precocious puberty
Excessive adrenal androgen effects in adulthood (males and females)
Males - no effect
Females: Masculinzation effects
Stimulus for adrenal androgen secretion:
ACTH
Inhibition of adrenal androgen release:
Cortisol
Clinical: If you are deficient in adrenal cortex secretions what 2 diseases are possible?
- Primary Hypoadrenalism (Addison’s)
2. Secondary Hypadrenalism
Clinical: If you have excess secretion of the adrenal cortex then what 4 diseases are possible?
- Cushing’s Disease
- Cushing’s Syndrome
- Excess androgens (adrenogenital syndrome)
- Primary hyperaldosteronism (Conn’s Disease)
What is the cause of Addison’s Disease?
Destruction of adrenal cortex
…So there is a loss of all adrenal cortex hormones
What do labs look like in Addison’s Disease? (2 significant findings)
- Elevated ATCH
2. Decreased levels of adrenal hormones (Aldosterone, Cortisol, Androgens)
Decreased aldosterone in Addison’s Disease causes:
Excessive excretion of sodium and water in urine
- -> Hypotension
- -> Hyponatremia
- -> Dec. blood volume…potential circulatory failure
Excessive retention of potassium and H ions
- -> hyperkalemia
- -> metabolic acidosis
Decreased glucocorticoids (cortisol) in Addison’s Disease causes:
Hypoglycemia…fatigue, loss of appetite
Decreased adrenal androgens in Addison’s Disease causes:
Female: dec. in pubic/axillary hair
Hyperpigmentation
Weakness, anorexia, wt loss, nausea
Cushing’s Syndrome =
excess cortisol of any pathology
- -> tumor secreting glucocorticoids
- -> Prolonged pharmaceutical administration of glucocorticoids
Cushing’s Disease =
Excessive ACTH with results in excess cortisol
–> tumor in pituitary produces excessive/elevated ACTH
–> May experience elevated mineralcorticoid and androgenic effects
Cushing’s Syndrome v. Cushing’s Disease
Cushing’s Syndrome is the excess of cortisol caused by any pathology whereas Cushing’s disease is specifically the excess of ACTH which in turn results in excess cortisol
5 Effects of increased glucocorticoids (cortisol)
- Poor wound healing
- Hyperglycemia…possible glycosuria
- Muscle wasting
- Osteoporosis
- Central obesity –> moon face, buffalo hump
1 effect of increased mineralcorticoids (Aldosterone)
Hypertension
Effects of increased adrenal androgens:
Virilization and menstrual disorders in females
Cause of Conn’s Syndrome
Tumor of adrenal cortex that secrete aldosterone
Primary Hyperaldosteronism is also known as:
Conn’s Syndrome
What is seen in a patient w/ hyperaldosteronism (Conn’s Syndrome)
- Hypertension
- Hypokalemia
- Metabolic Alkalosis
What does the Y chromosome secrete?
SRY antigen
The SRY antigen…
stimulates undifferentiated gonads to develop into testes
What duct does the SRY antigen develop and what does that duct develop into
Wolffian Duct
Develops into epididymis, vas deferens, seminal vesicle
What duct is inhibited by Y chromosome and what cells do this?
Sertoli cells of testes release MIH (Mullerian-inhibiting factor)
Prevents Mullerian duct from developing into female genitalia
What stimulates development of scrotum, penis and prostate gland?
DHT (dihydortesterone)
–> Prostate converts testosterone into DHT
DHT stimulates development of:
scrotum
penis
prostate gland
Describe how the Mullerian Duct and Wolffian duct are differentiated in the female
Since male hormone doesn’t release MIH, Mullerian Duct develops into fallopian tubes, uterus, vagina
Wolffian Duct is prevented from developing
What does the Mullerian Duct develop into?
Fallopian tubes
Uterus
Vagina
Function of Testes:
- Production of spermatozoa
2. Production of testosterone
What two hormones are required to produce sperm?
Testosterone and FSH
Where is testosterone synthesized?
Interstitial Cells of Leydig (of testes)
What are the anabolic effects of testosterone?
- Stimulate GH secretion leading to IGF-1 release
- End of puberty –> promotes mineralization of growth plates (“closure”)
- Stimulates protein synthesis in muscle
What are the androgenic effects of testosterone?
- Regulate development and maintenance of male accessory sex organs
- Differentiation of male reproductive tract and brain
- At puberty: development of secondary sex characteristics
- Role in libido and potency
- Testosterone gradually decreases with age…slow and constant
Function of ovaries
- Oogenesis - production of female germ cells
2. Produce estrogens and progesterone and inhibin
What happens to the uterus during menstration?
thickens endometrium
inc. uterine muscle contraction
What is the purpose of the menstrual cycle?
accelerate the maturation of the oviarian follicles (just before ovulation)
Estrogens play a role in: (6)
- Menstrual Cycle
- Fertilization
- Puberty
- Bone metabolism
- Blood chemistry
- CNS
Explain estrogen function in blood chemistry
Increase HDL and decrease LDL (BAD!!)
Inc. coagulation
Inc. sodium and water retention in kidneys
Progesterone Function: (2 major)
- Implantation and maturation of fertilized ovum
2. Maintain pregnancy
What is the major target tissue of progesterone?
Uterus
What does progesterone due once it binds to uterus receptors (4)
- Growth of endometrium
- Inc. blood supply to endometrium
- Relaxing effect on myometrium to promote implantation
- Elevate basal body temperature
Contraception and progesterone
Progesterone given during follicular phase inhibits fertilization by:
– Inhibiting LH –> inhibiting ovulation
– Inhibiting effects on cervical os and mucous plug
Progesterone and estrogen given in combination as contraceptives do what?
Prevent LH/FSH release
21 days on…5-7 days off to allow menstrual flow
High doses of progesterone can cause:
- Anesthetic effect on CNS
- Inc. susceptibility to epileptic episodes
- Inc. basal body temp
Dec. progesterone results in:
Influence mood
- -> PMS
- -> Postpartum depression
3 Phases of Menstrual Cycle
- Follicular Phase (Day 1-14)
- Ovulation (Day 14)
- Luteal Phase (Day 14-28)
Early Follicular Phase
1.) LH stimulates theca cells to produce androgens
FSH stimulates release of aromatase in granulosa cells
2.) Aratase converts androgens to estrogens
3.) Estrogens released from granulosa cell
4.) Estrogens diffuse into bloodstream or is stored in follicular cell
*Estrogen utilizes positive feedback!
Mid-follicular Phase
Dominant follicle emerges and continues to produce estrogen (+ feedback continues)
Aptosis of non-dominant follicles
Late-Follicular Phase
Estrogen levels increase and now have (+) feedback on release of LH
Surge of LH occurs
Ovulation (Day 14)
Surge in LH –> OVULATION
Ovum released from follicle
Luteal Phase (Days 14-28)
Follicle becomes corpus luteum
Corpus luteum secretes progesterone and estrogen and inhibin
–> inhibit release of FSH/LH (- feedback)
If fertilization hasn’t occured dec. progesterone and estrogen constrict blood flow to endometrium and leads to meneses
If fertilization occurs (pregnant):
Progesterone and estrogen levels stay elevated
Human Chorionic Gonadotropin (hCG)
What pregnancy tests look for
Released from syncytiotrophoblast
Functions of hCG
- Maintains production of estrogen and progesterone in corpus luteum until placenta can take over
- Suppress follicle maturation in maternal ovaries
What hormones does the placenta produce:
- Progesterone
- Estrogen
- CRH
- human Placental Lactogens (hPL)
Menopause
Ovarian tissue gradually ceases to respond to FSH and LH
Resutls in dec. estrogens and progesterone
Characteristics seen after menopause occurs:
- Reduction of secondary sex characteristics
- Atrophy breast tissue
- Thinning of pubic and axillary hair
- Mood changes
- Loss of bone density
- Loss of cardio functioning
