EXAM #2: ADRENAL PHYSIOLOGY Flashcards Preview

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Flashcards in EXAM #2: ADRENAL PHYSIOLOGY Deck (42):
1

Identify the main steroid hormones produced and secreted by each of the zones of adrenal cortex.

Glomerulosa= Aldosterone
Fasiculata= Cortisol
Reticularis= Androgens

2

Recognize and describe the control mechanisms of the hypothalamus-pituitary-adrenal (HPA) axis.

Hypothalamus= CRH
Anterior Pituitary= ACTH
Adrenal Cortex= Cortisol and Androgen production

3

What increases CRH secretion?

1) Stress
2) Circadian rhythms

4

When is CRH synthesis the highest?

AM

5

What is the mechanism by which ACTH increases adrenal steroid synthesis.

- ACTH activates receptors on cortical cells, specifically Melanocortin-2 receptor
- Steroidogenic enzyme expression is INCREASED

6

What cleaves cholesterol in the synthesis of the cortical steroids? What is the product?

Cholesterol Desmolase-- Pregnenolone

7

Pregnenolone is shunted down the Glucocorticoid and Androgen synthetic pathways by what enzyme i.e. what shunts this pathway to the left?

17 a-hydoxylase

8

After 3B hydroxysteroid dehydrogenase, what are the next two enzymes that continue the production of the Corticosteroids down their biosynthetic pathway?

21 hydroxylase and 11 B-hydroxylase

9

What converts adrostiendione to Testosterone?

17B-hydroxysteroid dehydrogenase

10

What enzymes are unique to producing Aldosterone?

Aldosterone synthase i.e. 18 hydroxylase and 18B-hydrox dehydrogenase

11

What is the major Glucocorticoid?

Cortisol

12

What is the rate limiting step of Cortisol/Glucocorticoid synthesis?

Cholesterol desmolase i.e. cholesterol to pregnenolone

13

What is the difference between the outcome of chronically low ACTH and elevated ACTH on the morphology of the adrenal gland?

Low= atrophy
High= hyperplasia

14

What are the major effects of increased cortisol? What is the mnemonic to remember these effects?

Cortisol is a BIG FIB

1) Blood pressure increased
2) Insulin resistance
3) Gluconeogenesis, lipolysis, proteolysis
4) Fibroblast activity increased
5) Immune system decreased
6) Bone resorption

*Cortisol increases beta-adrenergic receptors

15

How does cortisol increase blood glucose?

1) Increases enzymes and substrates (amino acids and adipose) that drive gluconeogenesis
2) Decreased glucose utilization by most cells

16

What is the main mineralcorticoid?

Aldosterone

*Note that some of the intermediates in the mineralcorticoid pathway have activity e.g. DOC

17

What is the name of synthetic aldosterone?

Fludrocortisone

18

What are the two major regulators that increase Aldosterone?

1) Angiostenin II
2) Elevated K+

19

What sets off the RAAS to ultimately increase ANGII?

Decreased renal perfusion pressure

20

What are the major effects of Aldosterone?

1) Increase Na+ and water reabsorption
2) Excretion of K+

21

In an enzymatic deficiency of Aldosterone, what is the expected response of Renin?

Increased Renin production

22

What are the two major actions of Aldosterone outside fo the kidney?

1) Conserve Na+ in sweating
2) Conserve/prevent loss of Na+ in stool

23

Describe the functions and physiological significance of both 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD type I) and 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD type II).

- Cortisol can bind mineralcorticoid receptor
- 11β-HSD type II inactivates cortisol to cortisone in mineralcorticoid rich tissues
- 11β-HSD type I activates cortisone to cortisol in glucocorticoid rich tissues

24

What are the physiologic effects of 17α-hydroxylase deficiency?

1) Increased mineralcorticoids
2) Hypokalemia
3) Increased blood pressure
4) Decreased cortisol
5) Decreased androgens

25

What is the clinical presentation of 17α-hydroxylase deficiency in males?

- Ambiguious genitalia
- Undescended testes

26

What is the clinical presentation of 17α-hydroxylase deficiency in females?

Lack of secondary sexual characteristics

27

What are the physiologic effects of 21-hydroxylase deficiency in males?

1) Decreased mineralcorticoids
- Increased K+
- Decreased BP
2) Decreased cortisol
3) Increased androgens

28

What is the clinical presentation of 21-hydroxylase deficiency in females?

- Salt wasting
- Females have male genitalia (virilization)

29

What lab is diagnostic for 21-hydroxylase deficiency?

17-OH progesterone

30

What are the physiologic effects of 11β-hydroxylase deficiency?

1) Decreased aldosterone but increased DOC (precursor mineralcorticoid)
- Increased K+
- BUT INCREASED BP
2) Decreased cortisol
3) Increased androgens

31

What is the clinical presentation of 11β-hydroxylase deficiency?

Virilization

32

What is the difference between Cushing's Syndrome and Cushing's Disease?

Disease= increased cortisol due to pituitary tumor
Syndrome= excessive endogenous or exogenous cortisol not from the pituitary

33

In Cushing's Disease, what is the expected result of a high dose dexamethasone suppression test?

50% reduction in ACTH and cortisol

34

In an adrenal adenoma, what is the expected result of a high dose dexamethasone suppression test?

No reduction in cortisol or ACTH

*ACTH will be low

35

In ectopic ACTH production, what is the expected result of a high dose dexamethasone suppression test?

No reduction in cortisol or ACTH

*ACTH will be high

36

In iatrogenic cushing's syndrome, what is the expected result of a high dose dexamethasone suppression test?

No reduction in ATCH or cortisol

*ACTH will be low

37

What catecholamine is predominantly produced by the chromaffin cells of the adrenal medulla?

Epinephrine

38

What enzyme catalyzes the rate-limiting step of catcholamine synthesis?

Tyrosine hydroxylase

39

How does NE get converted to Epi?

PNMT

40

What is required for the activation of PNMT?

Cortisol

41

Draw the major catabolic pathways of the catecholamines.

N/A

42

Which catecholamines have a greater effect at alpha and beta receptors?

Alpha= NE
Beta= Epi