pack Flashcards
What are the two parts of the adrenal gland and where are they derived from?
Adrenal cortex (80-90%)– glandular tissue derived from embryonic mesoderm
Adrenal medulla (10-20%)– formed from neural ectoderm, can be considered a modified sympathetic ganglion
What is the function of the adrenal cortex and what are its three zones and what does each zone produce?
Synthesizes and releases steroid hormones (corticosteroids)
Zones:
Zona glomerulosa – mineralocorticoids (mainly aldosterone)
Zona fasciculata – glucocorticoids +Androgens (mainly cortisol and corticosterone)
Zona reticularis – gonadocorticoids + glucocorticoids (mainly dehydroepiandrosterone DHEA)
What is the first step in converting cholestrol to a steroid hormone?
Conversion of Cholestrol to pregnenolone by dismolase
What are all the enzymes required to turn cholestrol to cortisol?
cholesterol desmolase, which converts cholesterol to
pregnenolone
17α-hydroxylase, which hydroxylates
pregnenolone to form 17-hydroxypregnenolone
3β-hydroxysteroid dehydrogenase, which converts 17-
hydroxypregnenolone to 17-hydroxyprogesterone;
21β-hydroxylase and 11β-hydroxylase, which
hydroxylate at C11 and C21 to produce the final
product, cortisol.
What happens if the 17a-hydroxylase step is blocked?
the zona fasciculata still can produce corticosterone without deleterious effect
What happens if there is a block at cholesterol desmolase, 3β -hydroxysteroid dehydrogenase, 21β -hydroxylase, or 11β -hydroxylase?
Blocks at the cholesterol desmolase, 3β -hydroxysteroid dehydrogenase, 21β -hydroxylase, or 11β -hydroxylase steps are devastating as they can prevent production of cortisol and corticosterone.
What are two examples of drugs that inhibit cortisol production and what is the mechanism behind them?
Example: Metyrapone and ketoconazole
Metyrapone: inhibits 11β -hydroxylase
Ketoconazole: inhibits several steps in the pathway including cholesterol desmolase, the first step.
What are the precursors of adrenal androgens and how are they converted to androgens?
17-hydroxypregnenolone and17-hydroxyprogesterone
converted: to androgens by removal of the C20,21 side chain.
Why does the zona glomerulosa not produce glucocorticoids?
The zona glomerulosa does not produce glucocorticoids for two reasons:
(1) Corticosterone, a glucocorticoid, is converted to aldosterone because this zone contains aldosterone synthase.
(2) The zona glomerulosa lacks 17α -hydroxylase and therefore
is unable to produce cortisol from progesterone
What are two steroids with mineralocorticoid activity other than aldosterone?
11-deoxycorticosterone, and corticosterone
What happens to mineralocorticoid production if the pathway is blocked below the level of 11-deoxycorticosterone?
Minerlocorticoids will still be produced
What are two enzymes that are below the level of 11-deoxycorticosterone?
aldosterone synthase and 11b-hydroxylase
What happens to mineralocorticoid production if the pathway is blocked above the level of 11-deoxycorticosterone?
then no mineralocorticoids
will be produced.
What is an enzyme that is above the level of 11-deoxycorticosterone?
21β -hydroxylase
Fill
What happens to cortisol, corticosterone, and aldosterone in 21-hydroxylase (P450c21) deficiency and what happens to ACTH and the adrenal cortex and what is a sign of it in women?
cortisol, corticosterone, and aldosterone: deficiency
ACTH increase Adrenal hypertrophy and high amounts of androgen
Virilization of female (masculanization)
What factors regulate zonae reticularis, fasciculata, and glomerulosa?
Zonae fasciculata/reticularis: hypothalamic-pituitary axis
Zona glomerulosa: ACTH and renin-angiotensin-aldosterone system.
What are the three ways that cortisol uses negative feedback to inhibit CRH?
Negative feedback is exerted by cortisol at three (1) Cortisol
directly inhibits secretion of CRH from the hypothalamus.
(2) Cortisol indirectly inhibits CRH secretion by effects on hippocampal neurons, which synapse on the hypothalamus. (3) Cortisol inhibits the action of CRH on the anterior pituitary, resulting
in inhibition of ACTH secretion.
What are the 4 mechanisims that regulate aldostrone secretion?
Renin-angiotensin mechanism – kidneys release renin, which is converted into angiotensin II that in turn stimulates aldosterone release
Plasma concentration of sodium and potassium – directly influences the zona glomerulosa cells
ACTH – causes small increases of aldosterone during stress
Atrial natriuretic peptide (ANP) – inhibits activity of the zona glomerulosa
What are the functions of glucocorticoids?
What is cushing syndrome
What is primary, secondary, and teritary adrenal insufficiency?
What is primary and secondary hyperaldostronisim?
What do the alpha and beta adrenergic receptors do?
