PHYS - The Adrenal Glands Flashcards
What are the actions of cortisol?
Lipolysis in adipose tissue
Gluconeogenesis in the liver
Muscle protein breakdown
Immunosuppression
Anti-inflammatory
When are cortisol levels highest?
Early in the morning, they are low in the late evening
What are the two pathways that signal aldosterone secretion?
Stress induces CRH secretion from hypothalamus
CRH signals ACTH secretion from anterior pituitary gland
ACTH promotes Aldosterone secretion
Decreased blood pressure detected in the kidney signals the secretion of Renin
Renin converts Angiotensinogen (synthesized in the liver) to Angiotensin I
ACE in the Lungs converts Ang I to Ang II
Ang II signals the adrenal cortex to secrete Aldosterone
What are the actions of aldosterone?
Aldosterone promotes the uptake of Na+ and water from the from the nephron, increasing blood pressure and fluid volume
What is Cushing’s Syndrome?
Umbrella term for excessive secretion of Adrenal Cortex hormones, particularly cortisol
However, in this class, Cushings SYNDROME refers to an adenoma of the andrenal cortex that is secreting excessive Cortisol
What is Cushing’s disease?
For the sake of this class, Cushings Disease is an adenoma of the anterior pituitary that is hypersecreting ACTH
What are the symptoms of Cushings Syndrome?
Moon Face, truncal obesity, buffalo hump, purple striations, hypertension, edema, weakness, osteoporosis, Hirsutism (upper lip hair on women), acne, diabetes, immunosuppression, cognitive effects
What is dexmethasone?
Dexmethasone is a drug that inhibits ACTH secretion from the anterior pituitary gland only (not from an exogenous source)
What is the purpose of a dexmethasone test?
Low dose tells confirms if a pt has CS. No response to low dose Dexmethasone is a positive result, but does not specify source of ACTH overproduction
High dose will suppress ACTH coming from the pituitary. If no change occurs, then you know that there is either an adenoma in the adrenal gland producing cortisol or there is an exogenous adenoma secreting ACTH
What is Addisons disease?
Primary Adrenal Insufficiency
Adrenal gland does not respond to ACTH or RAAS stimulation
No Aldosterone and No Cortisol Secretion
What causes addison’s and how do you treat it?
Addisons is caused by:
- Autoimmune attack on adrenal gland
- Adrenal hemorrhage
- Infection
- Tumor metastases to adrenal gland
Treated by supplementing adrenal hormones (cortisol and aldosterone)
What is Secondary Adrenal Insufficiency?
Adrenal insufficiency caused by lack of ACTH
Causes inhibition of cortisol secretion, but aldosterone secretion remains due to stimulation from the RAAS system
This is treated by supplemental cortisol only, since aldosterone is still being secreted
When does hyperpigmentation occur and why?
Whenever there is excessive ACTH production
ACTH is synthesized from POMC, which is also the source of alpha-MSH, which is the hormone responsible for melanin production
Increased ACTH synthesis means increased melanin production
Occurs in addisons (primary adrenal insufficiency)
What should the level of ACTH be for Cushings Syndrome?
Cushings Syndrome is an adrenal adenoma secreting Cortisol
Cortisol inhibits ACTH secretion, therefore ACTH levels would be low
If presented with a High Dose Dexamethasone test, ACTH levels would already undetectable, and cortisol levels would be unaffected
What should the ACTH levels be for Cushing’s Disease?
Cushing’s disease is a pituitary tumor secreting excessive ACTH, causing increased cortisol secretion
Would cause elevated levels of ACTH
If presented with a high dose dexamethasone test, ACTH levels would decrease, and so too would cortisol levels
