Exam 3 Steroid Synthesis Flashcards
(89 cards)
1
Q
Name androgens
A
testosterone
Dehydroepiandosterone ( DHEA)
Dihydrotestosterone
Androstenedione
2
Q
name a few estrogens
A
17 b estradiol (18 c estrogen)
3
Q
hormone that is required for embryo implantation
A
progesterone
- released from corpus luteum
- maintains uterine endometrium for implantation
4
Q
functions of DHEA
A
dehydroepiandosterone
- weak androgen, converted to its potent form in extra adrenal tissue
- inhibits G6PDH
- regulates NAD+ coenzymes
5
Q
DHEA is a precursor for what??? in ______
A
precursor for estrogen in POSTMENOPAUSAL women
6
Q
function of aldosterone
A
(secretion of K, absorption of Na)
- mineralocorticoid
secreted when version becomes hypovolemic
raises blood volume and blood pressure by promoting the reabsorption of sodium
7
Q
function of cortisol
A
- glucocorticoid
increases levels of glucose by increasing :
-gluconeogenesis in liver
-protein degradation in muscles - mobilization of fatty acids from adipose
8
Q
Which hormones are synthesized in adrenal glands
A
cortisol
aldosterone
DHEA
androstenedione
9
Q
which hormones are synthesized in gonads
A
17B estradiol
testosterone
DHT (dihydrotestosterone)*
progesterone
10
Q
what is the role of StAR
A
Steroidogenic acute regulatory protein
- transport protein that transports cholesterol* from cytosol* into mitochondria* (NOT the other way around)
11
Q
what is the rate limiting step in steroid biosynthesis,
where does it occur
A
cholesterol (c-27) —–> pregnenolone (c-21) + isocaproaldehude (c-6)
aka side chain cleavage of cholesterol
occurs in mitochondria
12
Q
enzyme responsible for RLS of steroid biosynthesis
A
desmolase (20-22 lyase)
type of p450 hydroxylase
13
Q
what is the role of 5a reductase
A
responsible for converting testosterone into dihydrotestosterone (much more potent)
located in smooth ER
14
Q
_____ converts testosterone into estradiol
where is it carried out
A
aromatase
- p450 hydroxylase
- in leydig cells
or via DHEA in follicular cells and mammary glands
15
Q
where is aldosterone
A
Zona Glomerulosa
16
Q
where is cortisol produced
A
zona fasciculata and zona reticularis of adrenal gland
17
Q
what are endorphins
A
compounds that bind to morphine receptors*
play a role in pain perception*
secreted from anterior pituitary gland
18
Q
hormones released by hypothalamus (6)/ function
A
-TRH (Tyrotropin releasing hormone)-
- GnRH (Gonadotropin Releasing Hormone)-
-CRH (corticotropin releasing hormone)
GHRH (growth hormones releasing hormone)
GHR (inhibitory)- somatostatin
PRL- prolactin inhibitor
19
Q
Function of TRH
A
thyrotropin releasing hormone
- stimulates release of tyrotropin and prolactin
20
Q
Function of GnRH
A
gonadotropin releasing hormone
-stimulates LH and FSH
21
Q
function of CRH
A
corticotropin releasing hormone
-stimulates release of ACTH and B-I endorphin
22
Q
function of GHRH
A
stimulates release of GH
23
Q
GHR inhibitor
A
somatostatin
- inhibits release of GH, glucagon and gastrin
24
Q
PRL inhibitor
A
Dopamine— (from median eminence)
- inhibits prolactin release
25
the most common enzyme in steroid biosynthesis*
Desmolase
26
conversion of cholesterol into pregnelone occurs in_______
mitochondria*
27
What is the second messenger that stimulates the synthesis and secretion of cortisol?
Camp
28
What is the second messenger that stimulates the synthesis and secretion of
aldosterone?
Phosphotidylinositol cascade.... IP3 and DAG
29
Name the second messenger that is produced as a result of atrial natriuretic factor
binding to kidney cells.
cGMP- second messenger
30
Guanylate cyclase catalyzes the formation of ____
cGMP
31
cholesterol esterase catalyzes formation of
cholesteroel
32
hormone that triggers synthesis and secretion of adrenal steroid is
ACTH
33
desmolase catalyses formation of____
pregnenonole
34
CYP is defined as
genes that encode for cytochrome P450 enzymes
35
Conversion of Angiotensin I to angiotensin II is by
Angiotensin converting enzyme ACE
36
in congenital adrenal hyperplasia the enzyme that is deficient is?
CYP21A2
| -cytochrome P450 steroid 21- hydroxylase
37
adrenal insufficiency causes___
addisons disease
38
2 reasons for Cushings syndrome
- prolonged exposure to glucocorticoids caused by usage of cortisol
- tumors of adrenal cortex
39
Name an adrenal steroid that causes HTN upon its overproduction.
minerolocorticoids-
| aldosterone
40
Aldosterone antagonist
spironolactone
41
name two Ace inhibitors
captopril, lisinopril enalapril
42
pregnancy is maintained by continuous secretion of progesterone which is stimulated by ____
LH
43
how is apoptosis stimulated during ovarial cycle?
Apoptosis is stimulated during ovarian cycle by the removal of the steroids estradiol and
progesterone.
44
testosterone to estradiol is catalyzed by?
aromatase
45
hormones that stimulate luteolysis
oxytocin and PGF2a
46
human placenta lacks which hydrolase enzyme
CYP17
47
testicular feminization is the result of?
5 alpha reductase
48
cortisol is transported from Adrenal to target tissue by
transcortin
49
transcortin binds to**
Target tissue of cortisol*
50
testosterone is transported by?
TEBP- testosterone estrogen binding protein
51
plasma protein that binds non specifically to steroids
albumin
52
2 compounds that inactivate steroids upon conjugation
- Glucouronides
- sulfates
ex- estradiol inactivated by conjugation with glucoroate
53
receptors for FSH LH gnRH angiotensin II and II are located on
plasma membrane
54
receptors for cortisol and aldosterone are located on
cell interior
55
receptors for testosterone, estrogen and progesterone are located in
nucleus
56
what are heat shock proteins
Heat shock proteins are cytosolic proteins that occlude the DNA binding region of the cortisol
and aldosterone receptors and cause the receptors to be inactive.
57
Define hormone response element
Hormone response element is a region of DNA to which a hormone receptor complex can bind
to and activate transcription.
58
glucocorticoids cause repression of
proopiomelanocortin gene
59
the active conformation of a steroid hormone receptor is a???
TRIMER
| not a dimer
60
Describe the DNA binding domain of hormone receptor.
The DNA binding domain of hormone receptors shares 6095% homology between steroid
receptor classes. They also contain Zn fingers.
61
what are Zn fingers
secondary structures in DNA binding domain that facilitate binding to DNA near the transcription initiation complex
62
What are the secretion signals for aldosterone, cortisol, testosterone,
17betaestradiol and progesterone respectively?
```
Aldosterone: Angiotensin II/III
Cortisol: ACTH
Testosterone LH
17- b-estradiol : FSH
Progesterone: LH
```
63
Name the bone forming and bone resorbing cells. Name some bone antiresorptive
compounds.
Osteoblasts (forming), Osteoclasts (resorbing). Antiresorptive compounds include,
bisphosphanates, alendronate (Fosamax), and risedronate (Actonel).
64
Name a catabolic product of estradiol the induces breast cancer.
16hydroxy estrogen (16OHEN) a side effect of Hormone Replacement Therapy for
osteoporosis.
65
What are the compounds that are being used in hormone replacement therapy (HRT)
treatment?
Equine estrogen, medroxy progesterone (progestin).
66
Name the universal sulfonate donor compound.
3'phosphoadenosine 5'phosphosulfate (PAPS).
67
BASIS of congenital adrenal hyperplasia
genetic defect decreasing cortisol
production, ACTH production unregulated, thus levels are high. Causes adrenal hyperplasia,
progesterone buildup (increase production of androgens/DHEA/androsteinedione), virilization in
females, precocious sex organ development in prepubertal males, or salt imbalance diseases
due to low aldosterone levels.
68
Addisons
Overall deficiency of adrenal steroids. ACTH levels are high.
Hypoglycemia due to low cortisol. Hypotension due to low mineralcorticoids.
69
Cushings
Prolonged exposure to glucocorticoids (due to antiinflammatory
use of cortisol or adrenal cortex tumors). Leads to high BSL, and truncal oesity with thin arms
and legs. May also exhibit hypertension.
70
HTN
```
Excessive secretion of mineralcorticoids from adrenal tumors.
Treated with Aldosterone antagonists (spironolactone)
ACE inhibitors (captopril, lisinopril, enalapril)
```
71
Osteoporosis
Estrogens induce synthesis of osteoprotegrin, which leads to
osteoblast differentiation. Lack of estrogen can lead to a reduction in bone mass, especially in
postmenopausal women.
72
Testicular feminization
Genetic deficiency in 5alphareductase, which
causes a reduction in DHT (an androgen that promotes the differentiation of male sexual
characteristics. XY with female gentalia (phenotypically, but do not actually have ovaries or
uterus).
73
Describe the role of fetal adrenal and fetal liver with reference steroid metabolism
during pregnancy.
Human placenta lacks CP17 (needed to make DHEA which is precursor to Estrogen). The Fetal
adrenal gland converts cholesterol to DHEA, then is transported to the fetal liver forming
16alphahydroxyDHEA. Aromatization will result in 17Betaestradiol.
74
Describe the process of estradiol mediated programmed cell death.
```
A drop of estradiol and progesterone result in the sloughing of the endometrium (menstration).
Degradative enzymes (proteases, nucleases, and lipases) are stimulated.
```
75
Describe atrial natriuretic factor (ANF) mediated signaling.
ANF comes from heart atrial cells that oppose the actions of angiotensin. Binds to Zona
glomerulosa cell receptors which activates guanylate cyclase leading to the formation of second
messenger cGMP from GTP. cGMP increases aldosterone synthesis and secretion.
76
Key enzymes in steroid metabolism
Cholesteryl esterase, Desmolase, Cytochrome P450 hydroxylase enzymes (17hydroxylase,
21hydroxylase, etc).
77
mechanism of p450 hydrozyase catalyzed reaction
cholesterol side chain cleavage
78
name 4 digestion related endocrine hormones
CCK
gastrin
GIP- gastric inhibitory peptide
secretin
79
4 cells that secrete the GIT hormoones
duodenal I cells- CCK
Antral G cells- gastrin
Duodenal K cells- GIP
S cells - Secretin
80
name the 2 families of GIT peptide hormones
Secretin family of peptides: includes secretin, glucagons, VIP and GIP.
Gastrin family of peptides: includes gastrin and CCK. Identical Cterminal sequences of first of 5
a.a.
81
Function of gastrin
stimulate release of HCL from parietal cells of stomach and regulate growth of mucosa
stimulated by food, inhibited by secretin and somatostatin
82
what is the secretion signal for CCK
CCK released in response to certain a.a. (tryptophan, phenylalanine), peptides released by
gastric proteolysis, acid pH, lipid and free fatty acids.
83
2 functions of CCK
CCK causes contraction of gallbladder to secrete bile acids and it stimulates the secretion of
pancreatic enzymes from the pancreas.
84
The functional part of the hormone, gastrin and CCK resides in the region of the
peptide.
Last five a.a. of the Cterminus.
85
name the secretion signal and function of secretin
Secretin is released in response to acidification (PH < 5) of the contents of the duodenum.
Secretin works to stimulate the secretion of pancreatic juice rich in bicarbonate.
86
Major hormone that causes NACL secretion is
VIP- vasoactive intestinal peptide
87
Guanylin promotes secretion of
NAcl
88
GIP stimulates secretion of
insulin
89
glucose stimulates secretion of?
GIP and therefore insulin
