Adrenal Gland 1

Question 1

What part of the adrenal gland secretes catecholamines?

Answer 1

Adrenal medulla located in the cetner of the adrenal gland

Question 2

What are the three zones of the adrenal cortex and what do they synthesize?

Answer 2

Zona glomerulosa - outer

Zona fasciculata - middle

Zona reticularis- inner

All three zones produce both pregnenolone and progersterone

Question 3

Where does the conversion of cholesterol to 11-deoxycorticosterone (DOC) occur?

Answer 3

Zona glomerulosa and Zona fasciculata

Question 4

What zone synthesizes aldosterone?

Answer 4

Zona glomerulosa

Only zone that expresses aldosterone synthase that converts DOC to aldosterone

Question 5

What is the functions of 11B-hydroxylase?

Answer 5

Converts DOC to corticosterone (cortisol) in the zona fasciculata

Question 6

What is enzyme P450c17?

Answer 6

Enzyme required for the synthesis of cortisol and androgen synthesis

Has 17a-hydroxylase and 17,20-lyase activities

Expressed in both the zona fasciculata and zona reticularis

Question 7

Where are glucocorticoids mainly synthesized?

Answer 7

Zona fasciculata with small amounts in the zona reticularis

Zona glomerulosa lacks 17a-hydroxylase activity so it is unable to synthesize cortisol and androgens

Question 8

Where are androgens mainly synthesized?

Answer 8

Zona reticularis

Question 9

How is transcription of StAR induced in the zona fasciculata and reticularis?

Answer 9

ACTH via a cAMP-dependent mechanism

Question 10

How is transcription of StAR induced in the zona glomerulosa?

Answer 10

Angiotensin II via Ca-calmodulin-dependent mechanism

Question 11

What is the effect off K on aldosterone synthesis?

Answer 11

K induces aldosterone synthesis in the zona glomerulosa via activation of VG-Ca channels

Question 12

What is the primary action of mineralcorticoids?

Answer 12

Maintain ECF volume by regulating Na reabsorption

Also promote K and H excretion

Principal mineralcorticoid is aldosterone

Question 13

What adrenal steroids have mineralcorticoid activity?

Answer 13

DOC and Cortisol

Aldosterone is quantitatively more important than DOC because of its large free fraction (40-50% compared to 5%)

Cortisol contributes very little to mineralcorticoid activity

Question 14

Why doesn’t cortisol contribute to mineralcorticoid activity?

Answer 14

It is converted to cortisone by 11B-HSD2

This enzyme is expressed in tissues with glucocorticoid receptors

Cortisol can cause hypertension if this enzyme is inhibited

Question 15

What is the principal adrenal androgen released by the zona reticularis?

Answer 15

Dehydroepiandrosterone (DHEA)

Secreted as DHEA sulfate (DHEAS)

High affinity for albumin

Small amounts of androstenedione are also released

Question 16

Why do DHEA and androstenedione have little androgen activity?

Answer 16

Low affinity for the androgen receptor

They are converted to more potent androgens peripherally

Question 17

Describe androgen production during pregnancy?

Answer 17

Fetal adrenal gland produces large amounts of DHEA sulfate, which is converted to estrogen by the placenta

Question 18

What layers is the fetal adrenal cortex composed of?

Answer 18

Neocortex

Fetal zone - source of DHEAS

Question 19

What is adrenarche?

Answer 19

Increase in circulating levels of adrenal androgens starting at 6-7 in girls and 7-8 in boys and continue to increase progressively through adolesence

Not invovled in the initiation of puberty

Question 20

What is the relationship between ACTH and adrenal androgens?

Answer 20

ACTH plays a role in regulating adrenal androgen secretion, but it is not the only factor

Adrenal androgens do not exert a negative feedback on ACTH secretion

Question 21

What is the state of circulating cortisol?

Answer 21

5-10% of circulating cortisol is free

75% bound to Corticosteroid binding globulin (CBG)

15% bound to albumin

Question 22

What is the most accurate measurement of daily cortisol output?

Answer 22

24-hour urinary excretion of unmetabolized cortisol

Question 23

Why do synthetic glucocorticoids have enhanced activity?

Answer 23

Increased receptor affinity

Delayed plasma clearance

Question 24

What is the principal physiological regulator of cortisol release?

Answer 24

ACTH

Released in secretory pulses throughout the day

Question 25

What are the acute actions of ACTH?

Answer 25

Increase hydrolysis of cholesterol esters Synthesis of StAR Increased blood flow to the adrenal cortex

Question 26

What are the chronic effects of ACTH?

Answer 26

Increase in growth and cell proliferation in the Zona reticularis and fasciculata Increased synthesis of steroidogenic enzymes, LDL receptors

Question 27

What results from long-term suppression of ACTH?

Answer 27

Adrenal gland atrophy Conversely, excessive ACTH production will cause adrenal gland hypertrophy

Question 28

How is ACTH release controlled?

Answer 28

CRH is the principal regulator of ACTH secretion

Question 29

What is the circadian pattern of cortisol release?

Answer 29

Diurnal rhythm Cortisol levels are highest in the morning upon awakening

Question 30

How does stress affect cortisol?

Answer 30

Stress increases cortisol release via the CNS CNS increases the activity of CRH-secreting hypothalamic neurons Also causes the release of vasopressin that potentiates CRH-mediated ACTH secretion Strong, overrides negative feedback control

Question 31

What is the negative feedback loop for cortisol?

Answer 31

Cortisol exerts a negative feedback effect on the hypothalamus and pituitary

Question 32

What is the permissive effect of cortisol?

Answer 32

Doesn't initiate processes specifically, but rather ensures the cell has the capacity to fully respond to stimuli by regulating the expression of certain genes for a particular process E.g. maintains glycogen synthase, therefore has a permissive effect on glucagon- and epinephrine-induced glycogenolysis

Question 33

How does cortisol protect against hypoglycemia?

Answer 33

Promotes gluconeogenesis via pathway enzyme production Mobilizes amino acids for use in gluconeogenesis Permissive effect on glycogenolysis

Question 34

What is the effect of cortisol on fat metabolism?

Answer 34

When present, promotes fat deposition in the trunk and face Permissive effect on enzymes necessary to support fat mobilization

Question 35

What are the metabolic effects experienced by hypo- and hyperadrenal patients?

Answer 35

Hypoadrenal - fasting hypoglycemia Glucocorticoid excess- hyperglycemic and hyperinsulinemic

Question 36

What are the cardiovascular effects of cortisol?

Answer 36

Required for normal responsiveness of blood vessels to vasoconstrictors Stimulates erythropoietin

Question 37

What are the nervous system effects of cortisol?

Answer 37

Mood, behavior, wakefulness and the perception of sensory signal intensity

Question 38

What are the developmental effects of glucocorticoids?

Answer 38

Alveolar maturation and surfactant production

Question 39

What are the effects of cortisol on calcium homeostasis?

Answer 39

Excess levels of glucocorticoids increases risk for osteoporosis Antagonize the effects of Vitamin D Inhibit renal Ca reabsorption Inhibits bone formation

Question 40

What are the anti-inflammatory actions of glucocorticoids?

Answer 40

Suppress the inflammatory response by blocking the expression of genes that code for pro-inflammatory cytokines Inhibit enzymes like phospholipase A2 and NO synthase Induces synthesis of Lipocortin (inhiibts PPLA2)