Hormones of the Adrenal Cortex (77)

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Name the 4 zones of the adrenal gland.

zona glomerulosa

zona fasciculata

zona reticularis

adrenal medulla

What is secreted by the zona glomerulosa?

mineralcorticoids (aldosterone)

What is secreted by the zona fasciculata?

glucocorticoids (cortisol)

What is secreted by the zona reticularis?

androgens (DHEA, androstenedione)

What is secreted by the adrenal medulla?

epinephrine

NE

How does cortisol affect CRH and ACTH secretion?

decreases both; 1

Describe the relase of corticotropin releasing hormone.

pulsatile, diurnal

During what time of day is cortisol release the greatest?

early morning

*plasma cortisol levels measured early morning; 2

Where is CRH synthesized?

paraventricular nucleus of hypothalamus

Is the half-life of CRH long or short?

short

What type of G protein is the CRH receptor?

Gs; 3

What is the precursor molecule for ACTH?

pro-opiomelanocortin (POMC); 4

What type of G protein is the ACTH receptor?

Gs; 5

What protein activates a cholesterol channel in the mitochondria, allowing it to enter and be converted into pregnenolone? In which zones does this protein act upon?

StAR; 6 (Steroidal acute regulatory protein)

zona fasciculata

zona reticularis

What is the short-term effect of ACTH?

conversion of cholesterol into pregnenolone

Name 2 long-term effects of ACTH.

transcription of synthesis enzymes

increase in number of LDL receptors

Describe the release of ACTH.

pulsatile and diurnal

Why is aldosterone production exclusive to the zona glomerulosa?

alone possesses aldosterone synthase

Name a hormone and ion that increase StAR in the zona glomerulosa.

angiotensin 2

high K+

What type of G protein is the angiotensin 2 receptor in the zona glomerulosa?

Gq; 7

How does high extracellular K+ affect synthesis and release of aldosterone?

increases synthesis and release of aldosterone; 8

How does aldosterone affect sodium, water, and K+ reabsorption/secretion?

9

Which parts of the nephron are affected by aldosterone?

principal cell of DCT/collecting duct

Name 3 channels in the principle cells of the distal convoluted tubule/collecting duct that are enhanced by aldosterone.

sodium pump

ENaC

K+ (ROMK) channels; 10

How does the body prevent cortisol from exerting a large mineralcorticoid effect?

11-beta-hydroxysteroid dehydrogenase converts cortisol into cortisone

Name a herb that blocks the enzyme 11-beta-hydroxysteroid dehydrogenase.

licorice

How can licorice affect sodium retention?

increase sodium retention, leading to hypertension--"Mineralcorticoid excess syndrome"

How does aldosterone secretion affect angiotensin 2 release?

negative feedback; 11

Explain how compensatory mechanisms in congestive heart failure can exacerbate the disease.

12

Name a cause of hypersecretion of aldosterone.

Conn's syndrome due to glomerulosa tumor

Describe K+, renin levels, and blood pressure in Conn's syndrome.

low renin levels

hypokalemia

increased blood pressure

Conn's syndrome Rx

aldosterone antagonists and surgical resection

Describe hydration, blood pressure, [Na], and [K] in hyposecretion of aldosterone.

dehydration

hypotension (marked postural hypotension due to low blood volume)

hyperkalemia

hyponatrema

Describe blood aldosterone, renin, and angiotensin 2 in hyposecretion of aldosterone.

decreased aldosterone

increased renin

increased angiotensin 2

Name the disorder: autoimmune disorder affecting the whole adrenal cortex.

Addison's disease

During what time of day is release of cortisol the greatest?

early morning

Name the plasma protein bound to cortisol in the blood.

cortisol binding globulin (transcortin)

Where in/on the cell are cortisol receptors found?

inside the cytoplasm. 13

Review actions of glucocorticoids.

14

How does cortisol affect insulin?

decreases effects of insulin on glucose uptake

How does cortisol affect protein metabolism?

increases proteolysis in all cells (except the liver)

How does cortisol affect fat metabolism?

increases lipolysis and mobilizes fatty acids

How does cortisol affect the immune system and inflammation?

immunosuppressive

anti-inflammatory

How does cortisol affect lysosomes?

stabilizes lysosomal membranes to prevent release of proteolytic enzymes

How does cortisol affect capillary permeability and tissue edema?

decreases both

How does cortisol affect synthesis of PGs and leukotrienes?

decreases both by decreasing phospholipase A2

Review anti-inflammatory/immunosuppressant effects of cortisol.

15

Review effects of cortisol on PGs and leukotrienes.

16

How does cortisol affect response to NE and angiotensin 2?

increases responses

What hormone is administered prior to premature births? Explain.

cortisol

increases surfactant production

Review actions of cortisol.

17

How does excess cortisol affect connective tissue?

loss of collagen and connective tissue

Describe 3 ways in which excess cortisol affects bone.

decreases formation and increases resorption

increases osteoclasts

increases PTH and Calcitrol on bone (increased resorption)

*causes osteoporosis

How does excess cortisol affect Ca metabolism?

decreases absorption from GIT

increases excretion by kidneys

*negative Ca balance

Name 4 causes of hypersecretion of cortisol.

19

What is the difference between Cushing's disease and syndrome?

Cushing's disease refers to increase release of ACTH from pituitary

Describe plasma ACTH and cortisol in Cushing's disease.

increased ACTH

increased cortisol

Describe plasma ACTH and cortisol in Cushing's syndrome.

low ACTH (negative feedback)

increased cortisol

Review manifestations of hypercortisolism.

18

What happens to the HPA axis of someone on chronic steroid therapy?

adrenal cortex atrophies because cortisol suppresses CRH and ACTH

Name 3 causes of primary adrenal insufficiency.

autoimmune

HIV/AIDS

TB

Describe a situation in which secondary adrenal insufficiency results.

sudden withdrawal of glucocorticoids after prolonged therapeutic use

Review clinical features of Addison's disease.

20

Describe blood pressure, [Na] and [K] in Addison's disease.

low bp

hyponatremia

hyperkalemia

Describe ACTH levels in Addison's disease.

high

Addison's disease Rx

replacement therapy with cortisol and a mineralcorticoid

Is cortisol or aldosterone production more affected in secondary adrenal insufficiency?

cortisol

ACTH has less effects on integrity of zona glomerulosa

What is the major androgen secreted by the adrenal cortex?

DHEA

What is the commonest enzyme deficiency causing hyposecretion of adrenal cortex hormones?

21-alpha-hydroxylase deficiency

Explain how low cortisol and low aldosterone can cause salt-losing virilizing congenital adrenal hyperplasia.

22

Salt-losing virilizing congenital adrenal hyperplasia Rx

reduce ACTH levels by giving glucocorticoid; 22

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