24 - Adrenal Glands Flashcards
where is the adrenal gland located
What type of organ
superior to kidney
a retroperitoneal organ
What are the three layers of the adrenal cortex
What do the layers do
secrete lipophilic steroid hormones that are essential for life
1) zona glomerulosa
2) zona fasciculata
3) zona reticularis
What is the zona glomerulosa
What controls
produces aldosterone (mineralcorticoid)
- alters Na+ and K+ balance
- helps adjust Bp and Bv
controlled by the renin-angiotensin-aldosterone (RAA) pathway/system
What is the aldosterone release stimulated by
dehydration
Na+ deficiency
hemorrhage
elevated K+
Describe the negative feedback system of aldosterone
1) stimulus
2) decrease in BV –> decrease in BP
3) Juxtaglomerular cells of kidneys
4) increased renin (enzyme)
5) angiotensin from liver
6) lungs convert angiotensin 1 to angiotensin 2
7) increased aldosterone in adrenal cortex
8) kidneys
- increased Na+ and water reabsoprtion and increased secretion of K+ and H+ into urine
9) increased BV
10) BP increases until it returns to normal (neg feedback)
11) vasoconstriction of arterioles
What is the zona fasciculata
What does it do
secretes glucocorticoids - stress hormones
- cortisol, cortisone, corticosterone
1) promote protein breakdown
2) promote lipolysis
3) promote glucose formation
4) promote resistance to stress
5) exert anti-inflammatory and immunosuppressive effects
How is glucocorticoid secretion regulated
negative feedback system
1) CRH stimulates release of corticotropin (ACTH)
2) ACTH stimulates secretion of cortisol by the adrenal cortex
3) elevated cortisol levels inhibit release of ACTH by the ant pituitary and CRH from the hypothalamus
What is the zona reticularis
secretes androgens
- primary androgen secreted is dehydroepiandrosterone (DHEA)
- androgens promote axillary and pubic hair growth and contribute to “growth spurts” during puberty
How does adrenal androgen differ in males and females
Males: adrenal androgen secretion is much less than testicular androgen secretion
Females: adrenal androgens contribute to libido (sex drive) and some are converted to estrogens by other tissues
- during menopause: all estrogens are derived from adrenal androgens
How is androgen secretion regulated
regulated by ACTH
no negative feedback on hypothalamus
1) Stimulus
2) CRH stimualtes release of corticotropin (ACTH)
3) ACTH stimulates secretion of androgens by the adrenal cortex
4) Androgens (DHEA)
5) tissue effect
What does the adrenal medulla represent
a modified sympathetic ganglion
How do the chromaffin cells release hormones
How are they regulated
lack axons –> release directly into the blood
regulated by neural input (splanchnic nerves) –> hormones released quickly
What are the types of stress
eustress
distress
What are the three phases of stress
alarm (f or f response)
- activation of sympathetic nervous system
resistance
- release of adrenal cortical hormones, growth hormone and thyroid hormone
exhaustion
- consequence of stress hormones that deplete body resources leading to msucle wasting, immunosuppression, gastric ulcers
What is the main cause of disease of the adrenal gland
excess or insufficient levels of cortisol
What is cushing’s syndrome
What are the causes
disorder caused by excessive levels of glucocorticoids (cortisol)
source of glucocorticoids may be
- endogenous (ACTH- secreting tumor, adrenal adenoma)
- exogenous (glucocorticoid administration)
What are the signs and symptoms of cushings
muscle wasting, atrophy (Catabolism)
moon face or buffalo hump (fat redistribution)
weight gain - central obesity, hyperlipidemia striae
hypertension
hyperglycemia
osteoporosis
susceptibility to infection
poor wound healing
What is adrenocortical insufficiency (addision’s)
what are the causes
disorder caused by insufficient secretion of glucocorticoids (cortisol) and mineralocorticoids (aldosterone)
autoimmune disorder
- destruction of the adrenal cortex or antagonism of the ACTH-receptors by autoantibodies
primary disease
- adrenal atrophy
secondary disease
- insufficient CRH or ACTH
withdrawl syndrome
What are the signs and symptoms of Addison’s
weight loss
hypoglycemia
weakness
decreased serum na
dehydration
hypotension
increased serum K+
cardiac arrhythmias
What is congenital adrenal hyperplasia (CAH)
what are the causes
rare, recessive, autosomal disorder (males and females equally)
due to an enzyme deficiency – cannot produce cortisol or aldosterone
pituitary homrones kick in, resulting in excess androgen production
What are the signs and symptoms of CAH
males:
- premature development of male characteristics
- early appearance of pubic and armpit hair
- severe illness within days of birth due to loss of salt (hyponatremia, hyperkalemia)
females
- virilization may occur
- hirsutism, clitoral enlargement, deepened voice, amenorrhea, breast atrophy, acne
What is the treatment for CAH
exogenous glucocoritcoid
salt replacement therapy
