Adrenal Gland Flashcards
Describe the location and shape of adrenal glands
- 2 triangular structures placed over each kidney
What is the adrenal gland composed of
- 2 separate endocrine tissues surrounding each other
- adrenal cortex , adrenal medulla on inside
- derived embryologically from different tissues
What is the function of the adrenal cortex and adrenal medulla
- Adrenal cortex: corticosteroids
- Adrenal medulla : catecholamines
Name the zones of the adrenal Cortex , types of hormones it secretes and what each zone secrete
- zona glomerulosa : mineralcorticoids
- zona fasiculata : glucocorticoids
- zona reticularis : adrenal androgens
- cortex secretes steroid lipophilic hormones that need to be transported in blood bound to plasma proteins
What are mineralocorticoids , give example
- hormone that regulates mineral and electrolyte balance in body
- ex: aldosterone
What are glucocorticoids , give example
- hormone that regulates blood glucose level and protein & fat metabolism
- ex: cortisol
What are adrenal androgens ,
- hormones responsible for masculinization
- important in children before puberty and adult women
Why are adrenal androgens not important in terms of male physiology
- because males already have testes that produce testosterone and responsible for masculinization
What is cortisol usually bound to
- corticosteroid binding globulin and albumin
What is aldosterone usually bound to
- albumin
what is androstenedione usually bound to
- albumin
Where are mineralocorticoids formed from and what stimulates it’s secretion
- cholesterol
- conversion of cholesterol to second step of mineralocorticoid pathway is influenced by ACTH
Where are the receptors of steroid hormones located
- inside the cell
Describe the composition and function of the adrenal medulla
- modified part of SNS
- adrenal medulla has no axon accompanying postganglionic sympathetic neurons in it so it releases chemical transmitter directly into blood
- releases adrenaline and noradrenaline
Why are chemical transmitters secreted in adrenal medulla called hormones
- because they are released into the blood and not transported by axons
What stimulates cortisol secretion
- physical stress ( ex: exercise )
- emotional
- chemical ( hypoglycaemia )
- extreme temperature
- diurnal rythme for cortisol secretion
Describe regulation of glucocorticoids secretion
- stress acts on hypothalamus to release CRH , which acts on anterior pituitary to release ACTH
- ACTH travels in blood to zona faciculata to stimulate glucocorticoids secretions ( cortisol )
- cortisol acts as negative feedback for ACTH and CRH secretion
What is the diurnal rhythm for cortisol ( same as ACTH )
- low levels of ACTH at night time
- and high levels before we get up in morning
Why are random cortisol measurements not helpful
- because cortisol follows the awake sleep diurnal rhythm
- could be reversed with people who work night shifts
How is cortisol measured , what would you see with normal cortisol levels
- in urine or saliva
- 85% of cortisol will be bound to transcortin in blood
- transcortin almost fully saturated
- free cortisol levels low
What would you find with high cortisol levels (3)
- transcortin quickly saturated
- greatly increased free cortisol
- Urinary free cortisol high ( UFC)
Actions of glucocorticoids ( in the 4 areas )
- muscle : break down protein in muscle tissue to amino acids = converted to glucose
- liver : gluconeogensis & glycogenesis ( only anabolic action )
- Fat cells : free fatty acid mobilization through lipolysis
- immune system : suppressed - anti-inflammatory
Give example conditions where glucocorticoids are given
- rheumatoid arthritis : to alleviate inflammation
- helps prevent organ rejection after transplant
Cortisol’s role to adaptation to stress
- promotes supply of glucose to tissue ( muscle & fat break down )
- permissive hormone : affects counter-regulatory hormones which counter insulin ( glucagon , adrenaline , GTH ) AND cortisol is required for expression of adrenergic & angiotensin II receptors in CVS
What is a permissive hormone
- hormone that needs to be present for other hormones to work optimally
Describe cortisol’s action on the CVS
- cortisol needs to be present for expression of adrenergic and angiotensin 2 receptors
- stop hypotension , hypovaleamia
Causes of glucocorticoids excess ( Cushing’s syndrome ) - 5 causes
- tertiary : hypothalamic tumour
- secondary : anterior pituitary tumour
- primary : adrenal tumour
- ectopic tumour ( outside of hypothalamus , pituitary , adrenal gland )
- iatrogenic Cushing’s syndrome : excessive use of exogenous glucocorticoids
What is the difference between Cushing’s syndrome and Cushing’s disease
- Cushing’s syndrome is anything that causes an excess of glucocorticoids
- Cushing’s disease is when an anterior pituitary tumour causes excess glucocorticoids
What would a patient with Cushing’s disease look like
- deposition of adipose tissue in face
- warm : pink cheeks
- deposition of fat in abdominal region & stretch marks
- very thin limbs
- bruising of skin : skin and walls of blood vessels begin to thin due to excess cortisol
- cervical fat pad : fat is mobilized to centre of body
Effects of Cushing’s syndrome on carbohydrate metabolism
- hyperglycaemia : increased blood glucose levels
- adrenal diabetes