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Endocrine Physiology > CH6 Adrenal Gland > Flashcards

CH6 Adrenal Gland Flashcards

1
Q

What two types of hormones does the adrenal gland secrete? What are they?

A

steroid hormones (glucocorticoids, mineralocorticoids, androgens), catecholamines (norepinephrine, epinephrine)

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2
Q

What kinds of steroid hormones secreted by the adrenal cortex? Which specific ones are secreted by which layer?

A

glucocorticoids (cortisol, zona fasciculata & zona reticularis in the cortex), mineralocorticoids (aldosterone, zona glomerulosa in the cortex), androgens (dehydroepiandrosterone DHEA, zona fasciculata & zona reticularis in the cortex)

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3
Q

What are the catecholamines secreted by the adrenal gland? What are they derived from? Which part secretes them?

A

norepinephrine, epinephrine; derived from L-tyrosine; secreted by medulla

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4
Q

What is the embryologic origin of the adrenal cortex?

A

mesodermal tissue

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5
Q

What is the embryologic origin of the adrenal medulla?

A

neural crest cells

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6
Q

What are the 3 zones of the adrenal cortex? what do they produce?

A

zona glomerulosa (mineralocorticoid aldosterone), zona fasciculata (glucocorticoid cortisol & androgen DeHydroEpiAndrosterone), zona reticularis (glucocorticoid cortisol & androgen DeHydroEpiAndrosterone)

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7
Q

What stimulates sex steroid release from adrenal glands?

A

hypothalamic-pituitary-adrenal hormone stimulation

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8
Q

What stimulates catecholamine release from adrenal glands?

A

direct sympathetic stimulation (sympatho-adrenal)

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9
Q

What is the circulation system of the adrenal gland?

A

superior, middle, & inferior suprarenal aa –> drain into adrenal medulla (allowing for steroid hormones released from cortex to influence catecholamine synthesis) –> renal vein (right drains into IVC, left drains into left renal artery)

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10
Q

What is the distinguishing feature of the outer layer of the adrenal cortex? What does it produce?

A

Zona Glomerulosa contains abundant smooth ER. produces mineralocorticoid aldosterone.

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11
Q

What is the distinguishing feature of the middle layer of the adrenal cortex? What does it produce?

A

Zona Fasciculata contains abundant lipid droplets. produces glucocorticoids cortisol and corticosterone, & also produces androgens Dehydroepiandrosterone DHEA and Dehydroepiandrosterone-sulfat DHEAS

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12
Q

What is the distinguishing feature of the inner layer of the adrenal cortex? What does it produce?

A

Zona Reticularis develops postnatally (approx. 3 yrs old). produces glucocorticoids cortisol and corticosterone, & also produces androgens dehydroepiandrosterone DHEA and dehydroepiandrosterone-sulfate DHEAS

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13
Q

Track Glucocorticoid Synthesis via progesterone.

A

(Cholesterol Ester Hydrolase) converts cholesterol-esters –> cholesterol. (P45side-chain cleavage enzyme) converts cholesterol –> pregnenolone. Pregnenolone –> Progesterone –> 11-deoxycorticosterone –> CORTICOSTERONE

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14
Q

Track Glucocorticoid Synthesis via 17-alpha-hydroxypregnenolone.

A

(Cholesterol Ester Hydrolase) converts cholesterol-esters –> cholesterol. (P450side chain cleaving enzyme) converts cholesterol –> 17-alpha-hydroxypregnenolone. 17-alpha-hyxroxypregnenolone –> 17-alpha-hydroxyprogesterone –> 11-deoxycortisol –> CORTISOL

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15
Q

Track Mineralocorticoid Synthesis.

A

(Cholesterol Ester Hydrolase) converts cholesterol esters –> cholesterol. (P450side chain cleaving enzyme) converts cholesterol –> pregnenolone. Pregnenolone –> progesterone –> 11-deoxycorticosterone –> corticosterone –> ALDOSTERONE

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16
Q

Why does Mineralocorticoid Synthesis only use the Progesterone pathway?

A

Zona Glomerulosa doesn’t have 17-alpha-hydrolase. (required to convert pregnenolone –> 17-a-OH-pregnenolone)

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17
Q

Track Androgen Synthesis via 17-alpha-hydroxypregnenolone.

A

(Cholesterol Ester Hydrolase) converts cholesterol esters –> cholesterol. (P450side chain cleaving enzyme) converts cholesterol –> pregnenolone. Pregnenolone –> 17-alpha-hydroxypregnenolone –> Dehydroepiandrosterone DHEA

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18
Q

Track Androgen Synthesis via 17-alpha-hydroxyprogesterone.

A

(Cholesterol Ester Hydrolase) converts cholesterol esters –> cholesterol. (P450side chain cleaving enzyme) converts cholesterol –> pregnenolone. Pregnenolone –> 17-alpha-hydroxypregnenolone –> 17-alpha-hydroxyprogesterone –> ANDROSTENEDIONE

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19
Q

What stimulates Glucocorticoid Cortisol release? What is an important feature of the stimulation of Glucocorticoid Cortisol release?

A

ACTH (corticotropin); it is pulsatile & follows a circadian rhythm that is sensitive to environmental & internal factors (light, sleep, stress, disease)

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20
Q

What kind of receptor does ACTH bind to? What kind of cell? What is the biological effect?

A

Gs protein-coupled plasma membrane melanocortin 2 receptor on Adrenocortical Cells. Activates PKA –> phosphorylates Cholesteryl-ester Hydrolase (increase activity) & activates + increase synthesis of Steroid Acute Regulatory (STAR) Protein. [both of these enzymes catalyze rate-limiting steps in steroidogenesis]

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21
Q

What is STAR protein? What is its significance?

A

STeroid Acute Regulatory Protein mediates cholesterol transfer to inner mitochondrial membrane for P450scc (side chain cleaving) enzyme [cholesterol–>pregnenolone]; this is one of the rate-limiting steps in steroidogenesis

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22
Q

What feedback mechanism regulates the Hypothalamic-Pituitary-Adrenal (HPA) Axis? What is the HPA axis?

A

HPA axis: circuit of CRH –> ACTH –> Cortisol; Cortisol inhibits release of CRH and ACTH

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23
Q

What is the binding protein for circulating Cortisol? What stimulates production of this protein?

A

glucocorticoid-binding alpha2-globulin (transcortin / cortisol-binding protein); stimulated by estrogen

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24
Q

What organs inactivate Cortisol?

A

liver, kidney

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25
Q

What is the inactive form of Cortisol?

A

Cortisol –> cortisone –> tetrahydrocortisol/tetrahydrocortosone (known as 17-hyxroxycorticosteroids)

26
Q

What is 11beta-hydroxysteroid Dehydrogenase?

A

NADP dependent reductase; 2 types: type I (cortisone –> cortisol), type II (cortisol –>cortisone)

27
Q

Which form of 11beta-hydroxysteroid dehydrogenase has a higher affinity for its substrate? What does it do?

A

type II, converts cortisol –> cortisone

28
Q

What is the purpose of aldosterone?

A

stimulate K+ excretion & increase Na+ resorption

29
Q

What stimulates release of aldosterone?

A

angiotensin II & high K+ concentration

30
Q

What does angiotensin II do?

A

vasoconstriction & stimulate aldosterone

31
Q

What is the renin-angiotensin-aldosterone system a response to?

A

decrease of blood volume

32
Q

What do the adrenal androgens (DHEA / DHEAS) get converted into? What happens to that hormone?

A

DHEA/DHEAS –> androstenedione –> dihydrotestosterone OR 17beta-estradiol

33
Q

What are the 2 types of steroid hormone receptors?

A

type I (mineralocorticoid receptor) & type II (corticosteroidreceptor)

34
Q

What is special about type I steroid hormone receptor?

A

specific for mineralocorticoids, but have a high affinity for glucocorticoids

35
Q

How is the specificity for type I steroid hormone receptor enhanced?

A

1) glucocorticoids are bound to glucocorticoid-binding-alpha2-globulin & albumin. 2) aldosterone target cells have 11beta-hydroxysteroid-dehydrogenase-type-II activity. 3) mineralocorticoid receptor discriminates between aldosterone and glucocorticoids (glucocorticoids dissociate faster than aldosterone from type I receptors)

36
Q

What is the overall effect of Glucocorticoid Cortisol?

A

increase blood glucose concentration

37
Q

How does cortisol effect blood vessels?

A

maintain vascular integrity/fluid volume & responseiveness ot catcholamine

38
Q

How does cortisol effect immune function?

A

anti-inflammatory effect

39
Q

What is the physiological effect of Aldosterone on the distal tubule Principal Cells?

A

increase synthesis of Na+ (in) channels & K+ (out) channels in apical membrane. increase Na+/K+ 3:2 ATPase in basolateral membrane

40
Q

How does Aldosterone effect the pH of urine?

A

makes urine more acidic and plasma more alkaline (increase expression of H+-ATPase and Cl-/HCO3 exchanger of intercalated cells)

41
Q

What other important areas are receptors for Aldosterone (type I MC steroid receptors) located?

A

salivary glands, sweat glands (increase Na+ intake), colon (increase K+ excretion)

42
Q

How does 21-hydroxlase deficiency present? why?

A

virilization (androgen excess), sodium wasting, accumulation of DHEA & ACTH; no glucocorticoid or mineralocorticord activity (prevent progesterone from forming 11-deoxycorticosterone & prevents 17alpha-hydroxyprogesterone from forming 11-deoxycortisol)

43
Q

How does 11beta-hydroxlase deficiency present? why?

A

virilization (androgen excess), salt/water retention, hypertension; has mineralocorticoid activity (accumulation of 11-deoxycortisterone, 11-deoxycortisol, DHEA, ACTH)

44
Q

What is Cushing Syndrome?

A

excess ACTH resulting in excess cortisol (can be ACTH dependent or independent based on CRH:ACTH)

45
Q

What is Addison Disease?

A

glucocorticoid & mineralocorticoid deficiency (can see regular mineralocorticoid b/c it can be stimulated by angiotension II/K+)

46
Q

What is Conn Syndrome?

A

tumor of adrenal gland causes hypersecretion of aldosterone (hypertension, hypokalemia)

47
Q

What causes secondary hyperaldosteronism?

A

excess renin-angiotensin system stimulation of aldosterone

48
Q

What is Pseudohyperaldosteronism?

A

activation of type I steroid hormone receptor (mineralocorticoid) by other substances (e.g. glucorticoid resistance)

49
Q

What is Primary Hypoaldosteronism?

A

adrenal cannot produce aldosterone; see elevated renin activity

50
Q

What is Secondary Hypoaldosteronism?

A

inadequate stimulation by angiotensin II (usually associated with renal insufficiency

51
Q

What is Pseudohypoaldosteronism?

A

unresponsiveness of steroid receptor I to mineralocorticoid hormones (sever salt wasting, hyperkalemia, metabolic acidosis)

52
Q

What substance stimulates the adrenal medulla?

A

acetylcholine

53
Q

What kind of cells is the adrenal medulla made of?

A

Chrommafin Cells (aka pheochromocytes)

54
Q

How is Epinephrine formed?

A

Tyrosine –> DOPA (via tyrosine hydroxylase). –> Dopamine (via dopa decarboxylase) –> Norepinephrine (via dopamine-beta-hydroxylase) –> Epinephrine (via phenylethanolamine N-methyltransferase)

55
Q

What are catecholamines metabolized by? What do they become for excretion?

A

COMT (cathol-o-methyltransferase) & MAO (monoamine oxidase), excreted as VMA (vanillylmandelic acid)

56
Q

What types of receptors do catecholamines bind to?

A

alpha/beta adrenergic G protein-coupled receptors

57
Q

What type of receptor are alpha adrenergic receptors? What do they have a high affinity for?

A

Gq, epinephrine

58
Q

What type of receptor are beta adrenergic receptors? What do they have a high affinity for?

A

Gs, isoproterenol (asynthetic agonist)

59
Q

What important role does the beta adrenergic receptor play in the heart?

A

increase contractility

60
Q

What receptors does Isoproterenol target?

A

B1-adrenergic receptor

61
Q

What receptors do bronchodilators target?

A

B2-adrenergic receptor

Endocrine Physiology (15 decks)

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