Adrenal Gland Flashcards
Adrenal cortex releases what kind of hormones?
Steroid hormones
Three layers of adrenal cortex
Zona glomerulosa
Zona fasiculata
Zona reticularis
What hormones do the Zona fasiculata secrete?
Glucocorticoids
What Zona secretes mineral corticoids?
Zona glomerulosa
What hormones does Zona reticularis secrete?
Weak androgens
What does adrenal medulla secrete?
Catecholamines
Example of mineralocortcoids:
Aldosterone
Example of glucocorticoid:
Cortisol
Example of androgens:
DHEA
What is the name for excessive glucocorticoids?
Cushings syndrome
Name for excessive Mineralocorticoids?
Conns syndrome
Name for excess Catecholamine from medulla?
Phaeochromocytoma
What is the group of genetic disorders that affect the adrenal glands called?
Congenital adrenal hyperplasia
Names of some adrenal tumours
Adrenal incidentaloma
Adrenocortical carcinoma
What are corticosteroids?
Any group of steroid hormones produces by adrenal cortex
Mineralocorticoids
Glucocorticoids
Weak androgens
Features of corticosteroids:
Lipid soluble
Bind to specific intracellular receptors
Exact action depends on structure
How do corticoids produce their effects?
Lipid soluble - passes through cell membrane
Bind to Intracellular receptors
By altering gene transcription directly/ indirectly
All steroid hormones have what precursor
Cholesterol
Why are glucocorticoids essential to life?
Important to homeostasis
Conditioning the body’s response to stress
What are the actions of glucocorticoids like?
Actions on most tissues
“Permissive” - do not directly initiate but allow other factors to be present
Actions of glucocorticoids that increase glucose mobilisation?
Augment gluconeogenesis
Amino acid generation
Increased lipolysis
Actions of glucocorticoids that maintain circulation
Vascular tone
Salt and water balance
Actions of glucocorticoids that allow immunomodulation
Immunosuppression
Anti inflammatory
Transport of glucocorticoids in circulation
heavily bound to proteins
What is the percentages of glucocorticoids bound to proteins in the blood?
90% bound to CBG
5% bound albumin
5% free glucocorticoids (bioavailable)
Regulation of glucocorticoids (hormones and glands involved)
Via CRH released from the hypothalamus
Then ACTH released from anterior pituitary gland
Physical Effect of ACTH deficiency on adrenal
Becomes atrophic and shrinks
2 ways of Circadian rhythm of circulating cortisol
Diurnal - occurring during daylight hours
Circadian - occurring once every 24 hrs
What causes stress on the body?
Infection
Trauma
Haemorrhage
Medical illness
Psychological
Exercise/ exhaustion
How does negative feedback work in the adrenal gland?
When there are high cortisol levels, cortisol binds to glucocorticoid receptors in the pituitary gland and hypothalamus
Negatively feeds back
Then CRH and ACTH secretions inhibited
What are the main Mineralocorticoids?
Aldosterone
DOC
Why are Mineralocorticoids important?
Critical to salt and water balance in certain organs
Where do Mineralocorticoids act?
Kidney
Colon
Pancreas
Salivary glands
Sweat glands
Other effector organs of sodium reabsorption for mineralocorticoids
Sodium resorption in
Pancreas
Sweat glands
Salivary glands
Colon
Non classical effects of mineralocorticoids:
Myocardial collagen production
Role in cardiac fibrosis/ remodelling
Cortisol binding in non stressed state:
Lots of cortisol bound to CBG
Most remains in intravascular space
Cortisol binding in stressed state:
CBG cleaved
Increased amount of free cortisol
More movement of cortisol outve blood vessels into cell cytoplasm
Physical Effect of excess ACTH on adrenal glands:
Large adrenal glands (adrenal hyperplasia)
Where are glucocorticoid receptors found?
In pituitary gland and hypothalamus
So negative feedback can be stimulated
What is the effect of general surgery on cortisol levels
Massive increase of cortisol during surgery remains high for a few days (loss of diurnal variation)
Feedback is lost
Stress cytokines repeatedly stimulate CRH and ACTH - increased cortisol
Reduced synthesis and breakdown of CBG
What is the percentage activity of DOC compared with aldosterone?
3%
Regulation of mineralocorticoids via renin-angiotensin aldosterone system:
Juxtaglomerular cells of kidney prod renin due to reduced renal blood pressure
Renin converts angiotensinogen to angiotensin I in liver
Angiotensin I converted to angiotensin II by ACE
Ang II stimulates aldosterone release by binding to AT1 receptors
How does regulation for mineralocorticoids by renin angiotensin aldosterone system (RAAS) increase BP
Angiotensin stimulates aldosterone release by binding to AT1 receptors
Causes sodium and water retention
Increases blood volume
Increases BP
Loss of aldosterone results in lower free liquid
What do aldosterone and cortisol have in common?
Both bind and have equal affinity to mineralocorticoid receptor
Why aren’t mineralocorticoid receptors swamped with cortisol even though it is more abundant than aldosterone?
11Beta- HSD2 (hyrdoxysteroid dehydrogenase 2) enzyme in kidney converts cortisol to cortisone
Cortisone cannot bind to MR
Why does excess liquorice cause mineralocorticoid excess syndrome
Inhibits 11Beta-HSD2 enzyme which converts cortisol to cortisone in the kidney
So more cortisol to bind to MR
Excess activation of MR
What are the major source for androgens in women
Adrenal glands
Connection between adrenal glands and post menopausal women
Glands prod oestrogen precursor in post menopausal
What is Androstenedione?
Androgen
Precursor for testosterone
More androgenic than DHEA but only 1/10th of testosterone
What hormone regulates the production of adrenal androgens
ACTH
How is the adrenal medulla involved in sympathetic release of catecholamines (not essential to life)
Acts as a specialised ganglion
Supplied by sympathetic pre ganglionic neurones
Stimulate chromaffin cells to synthesise and release catecholamines (adrenaline/ noradrenaline)
What has a relatively large effect on the production of catecholamines
High Cortisol has a permissive action on production catecholamines
What is the ratio of adrenaline: noradrenaline produced
80:20