Hypothalamic-pituitary-adrenal Axis Flashcards
What is the HPA axis mainly concerned with
Production of steroid hormones from adrenal cortex
Of the HPA axis, what does the hypothalamus release
CRH
Of the HPA axis, what doesthe anterior pituitary release?
ACTH
In the HPA, what does the adrenal cortex release
ACTH from anterior pituitary stimulates the release of cortisol and aldosterone from the adrenal cortex
What kind of feedback is there in the HPA axis
Both short and long loop
- ACTH inhibits CRH release
- cortisol levels inhibit ACTH and cortisol levels
Cortisol during time of fasting
- is a stress hormone in times of fasting
- maintains blood glucose levels
- increases protein catabolism
- increases FA utilization
- reduces inflammation and suppresses the immune system
A secondary hypercortisolism would present with
Low levels of CRH
Where do the adrenal glands sit
On top of the kidneys
What are the two main divions of the adrenal glands
Medulla and cortex
What does the adrenal medulla do
Makes epinephrine and norepinephrine
What are the divisions of the adrenal cortex
- zona glomerulosa
- zona fasciculate
- zona reticularis
What part of the adrenal cortex makes aldosterone
Zone glomerulosa
What part of the adrenal cortex makes cortisol and androgens
Both the zona fasciculate and the zona reticularis
What parts of the adrenal cortex are important for the HPA axis
Zona fasciculate and zona reticularis
What is the outermost layer of the adrenal cortex
Zona glomerululosa
What are medullary hormones made from
Tyrosine
What are Adrian cortex hormones derivatives of
Cholesterol
Synthesis of hormones in the adrenal cortex
- cortex contains the enzymes to make all necessary hormones
- stimulated by ACTH
- disruption can lead to excess production of others
What happens when there is a disruption of the pathway of one of the adrenal hormones?
Results in excess production of other hormones
21B hydroxylase deficiency
- loss of aldosterone and cortisol production
- overproduction of androgens (causes masculinization)
What do low levels of cortisol and aldosterone do to ACTH levels
Increases them
In a male with an ACTH deficiency, which of the following hormones would be affected the most
Aldosterone
Regulation of glucocorticoids (cortisol) and adrenal androgens
- normally pulsatile
- controlled by circadian rhythm
- normally no exogenous control
When do levels of adrenal hormones rise?
Right before waking and peak after
- this prepares the body to wake up and move prior to a meal
- raises blood glucose and mobilizes other energy stores
What is difficult for a persons to do that has hypocortisol
Get out of bed
What is a powerful stimulus for cortisol
Stress
-can cause weigh can and illness
ACTH stimulators factors
- decreased blood cortisol levels !!
- sleep-wake transition
- stress; hypoglycemia; surgery; trauma
- psychiatric disturbances
- ADH
- alpha adrenergic agonists
- B adrenergic antagonists
- serotonin
ACTH inhibitory factors
- increased blood cortisol levels
- opioids
- somatostatin
What are mineralocroticoids (aldosterone) controlled by
RAAS
Blood potassium levels (need ANgII to make it)
Mechanisms of mineralocroticoids (aldosterone)
- retain water and sodium
- secrete potassium and H
Cortisol and blood glucose
Maintainence of blood glucose levels
Mechanism of actions of cortisol and blood glucose levels
Stimulates gluconeogenesis by liver
- liver produces glucose from other sources like fat, protein
- causes muscle breakdown to provide Amina acids to liver
Other than gluconeogensis, what else does cortisol do
It is antiinflammatory and immunosuppressant
- inhibits production of inflammatory molecules
- inhibits proliferation of lymphocytes
- inhibits platelet activation
Which of the following would be true of someone with loss of both cortical hormones (aldosterone and cortisol)
Low blood volume and low blood glucose
What are the main pathologies of the adrenal gland
- Addison’s disease
- Cushing disease
- conn syndrome
- congenital adrenal hyperplasia (21B hydroxylase deficiency and 17a hydroylase deficiency)
Addison’s disease
Primary hypocorticolism
-adrenal gland does not make enough cortisol
Symptoms of Addison’s disease
- hypoglycemia and weight loss
- muscle weakness
- hypotension, hyperkalemia
- metabolic acidosis
- hyperpigmentation
Hyperpigmentation due to Addison’s disease
- ACTH and MSH come from same protein
- MSH causes activation of melanocytes and skin darkening
- bronze skin and dark gums
What is the difference between Cushing’s syndrome and Cushing’s disease
Cushing’s syndrome is a primary hypercortisolism
Cushing’s disease is a secondary hypercortisolism
Cushing’s syndrome
Primary hypercortisolism
-adrenal cortex makes too much cortisol
Cushing’s disease
Secondary hypercortisolism
-anterior pituitary makes too much ACTH
What are the symptoms of Cushing’s
- hyperglycemia, weight gain
- central obesity, moon face, buffalo hump
- muscle wasting
- hypertension
- striae (huge stretch marks)
- virilization in females (masculinization)
What is the virilization in Cushing’s from
Due to overflow into androgen production, more so in secondary
Will someone with Cushing’s have high aldosterone
Not really. If there is a reason to need aldosterone they may have a larger than normal amount of it released, but overall not too much floating around
Conn syndrome
Aldosterone secreting tumor
-primary hyperaldosteronism
Symptoms of conn syndrome
Hypertension
Hypokalemia
Alkalosis
Dysfunction in one of the enzymes required for adrenal function
Congenital adrenal hyperplasia
-hyperplasia and hypertrophy compensate
21B hydroxylase deficiency
- congenital adrenal hyperplasia
- loss of both cortisol and aldosterone
- virilization in both sexes
17a hydroxylase deficiency
- congenital adrenal hyperplasia
- loss of cortisol and adrenal androgens
- over production of aldosterone
Which congenital adrenal hyperplasia results in the loss of cortisol and aldosterone
21B hydroxylase deficncy
Which congenital adrenal hyperplasia results in the loss of cortisol and adrenal androgens
17a hydrozylase deficiency
Which is more severe, 21B H deficiency or 17a H deficiency
21B hydroxylase deficiency
How would you differentiate between Cushing’s syndrome and Cushing’s disease
ACTH levels
