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S3B2 Biochemistry > Hormones 4 & 5 > Flashcards

Hormones 4 & 5 Flashcards

1
Q

What steroids are secreted by the adrenal glands?

A

cortisol

aldosterone

androgens (DHE, andorstenedione)

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2
Q

What steroids are secreted by the testis?

A

testosterone

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3
Q

What steroids are secreted by the ovary?

A

estrogens (estradiol, estriol, estrone)

progesterone

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4
Q

All steroids are derived from what precursor?

A

cholesterol

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5
Q

What is the rate-limiting step in producing steroid hormones from cholesterol?

This is performed by what enzyme?

A

irreversible cleavage of 6-carbon residue from cholesterol (removal of the side-chain)

producing pregnenolone (C21) + isocaproaldehyde

cholesterol-20,22-desmolase or P450 side chain cleavage (mitochondrial enzyme)

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6
Q

How is cholesterol transported to the mitochondria?

This transport is regulated by what variable?

A

STAR (steroidogenic acute regulatory protein) transports cholesterol to mitochondria

ACTH-dependent (in adrenal)

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7
Q

What are the 3 tissue regions found in the adrenal cortex?

A

zona glomerulosa

zona fasciculata

zona reticularis

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8
Q

Adrenal cortex produces what 3 major classes of steroid hormones?

Where in the cortex are each of them produced?

A
  • Mineralcorticoid (aldosterone)
    • zona glomerulosa
  • Glucocorticoid (cortisol)
    • zona fasciculata
  • Androgens (DHEA, AD)
    • zona reticularis
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9
Q

What is the function of aldosterone?

A

regulates body levels of sodium & potassium

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10
Q

What is the function of coritosol?

A

regulates carbohydrate metabolism

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11
Q

What is the function of DHEA / AD?

A

similar to the actions of steroids produced by the male gonads

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12
Q

What enzyme is only located in the zona graunulosum is respondible for mineralcorticoid synthesis?

A

aldosterone synthase

(18-hydroxylase and 18-hydroxydehydrogenase)

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13
Q

What enzymes are important in the synthesis of glucocorticoids in the zona fasciculata?

A

17 alpha-hydroxylase

(part of P450c17)

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14
Q

What enzymes are important in the synthesis of androgens in teh zona reticularis?

A

17,20-lyase or 17,20-desmolase

(part of P450c17)

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15
Q

What proteins bind steroids in the blood for transport?

A

CBP (corticosteroid binding alpha2-globulin) or transcortin

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16
Q

Where is transcortin produced?

A

liver

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17
Q

Describe the general percentage of how cortisol of found in the blood?

What st he percentage of bound aldosterone?

A
  • Cortisol
    • 75-80% CBP (1:1 binding)
    • 15% albumin
    • 5-10% “free”
  • Aldosterone
    • 50-70% bound to CBP or albumin
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18
Q

What disease occurs with insufficient prouction of steroid hormones from the adrenal gland?

A

Addison’s disease

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19
Q

What condition is due to high cortisol exposure for an extended period of time?

A

Cushing syndrome

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20
Q

What is the disease that results from a pituitaty tumor producing too much adrenocorticotropic hormone?

A

Cushing disease

(specific kind of Cushing syndrome)

(secondary hypercortisolism)

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21
Q

Which cells in the testis produce testosterone?

What is the rate-limiting step of its synthesis?

It is regulated by what hormone?

A

Leydig cells

STAR is rate-limiting step

stimulated by LH

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22
Q

What is the key enzyme in testosterone production?

A

17beta-hydroxysteroid dehydrogenase

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23
Q

Testosterone is essential for what developmental features?

A

male secondary sexual characteristics

ie.

hoarse voice, moustache, muscular body, male libido

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24
Q

Where is dihydrotestosterone produced?

Catalyzed by what enzyme?

How does its potency compare to testosterone?

A

peripheral tisues

5 alpha-reductase

more potent than testosterone

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25
Where is androgen-binding protein produced? Its production is stimulated by what signals? What is its function?
Sertoli cells stimulated by testosterone and FSH locatd within testes to maintain high concentration of total androgens
26
Describe regulation of testosteone secretion from the hypothalamus to spermatogenesis.
* **Hypothalamus** secretes gonadotrpin-releasing hormone (**GnRH**) * **GnRH** stimulates the **anterior pituitary** to release **FSH** and **LH** * **LH** stimulates interstitial (**Leydig**) cells to produce **testosterone** * **FSH** activates testis for **spermatogenesis** This is an example of a negative feedback loop
27
What part of the primary femal sex organ secrtes estrogen? What is the primary form of estrogen that it secretes? Its release is stimulated by what signal?
folicle 17beta-estrdiol FSH
28
How do peripheral female tissue produce estrogens?
from androgens
29
Describe regulation of estrogen secretion from the hypothalamus to ovulation.
* They **hypothalamus** secretes **GnRH** * **GnRH** stimulates the **anterior pituitary** to secrete **FSH** and **LH** * **FSH** stimulates **follicle developmen**t in the ovary * **LH** stimulates **ovulation** This is an example of a negative feedback loop
30
What hormone is the startign material for estrogen?
testosterone
31
Describe what is happens during menstruation in the following tisues Pituitaty level Ovary level Endometrial level
* **Pituitaty level** * **FSH** level _increases_ * **LH** level surges _one day before ovulation_ & after ovulation to maintains its level * **Ovary level** * **FSH** stimulates _follicule development_, which starts secreting **estrogen** * A day after _LH surg_e, **ovulation** takes place. Once egg is released, remaining follicle is known as corpus luteum. * **LH** acts on _corpus luteum_ & stimulates **progesterone** production * **Endometrial level** * **Estrogen** stimulates _endometrial layer growth_ * After ovulation, **progesterone** causes endometrial thinning (secretary gland)
32
What is the proposed cause of PMS? What are the symptom? It affects what percent of people with uteruses?
drop in estrogen & progesterone levels the week before a period headaches, mood swings, other physical and emotional changes 85% of women
33
What is PMS called when it dirupts work of personal relationships?
premenstrual dysphoric disorder (PMDD)
34
Sex hormones bind to proteins produced in what organ? Describe the percent of androgens and estogens bound to various proteins in the blood?
liver-derived * androgens * 65% testosterone bound to sex hormone-binding globulin (SHBG) * 34% bound to albumin * 1-2% free * estrogens * 60% bound to SHBG * 20% bound to albumin * 20% free
35
Where is the main site of steroid excretion? How does it occur?
liver steroid ring structure is not broke Conjugation: glucuronidation & sulfation
36
Identify the type of horomone & the function: estrogens
steroids maintenance of pregnancy
37
Identify the type of horomone & the function: progestins
steroids mimic action of progesterone
38
Identify the type of horomone & the function: chorionic gonandotropin
2 subunits (alpha & beta) activity similar to LH
39
Identify the type of horomone & the function: placental lactogen
protein acts like prolactin and GH
40
Identify the type of horomone & the function: relaxin
2 proteins produced in ovarian corpus luteum, inhibits myometrial contractions, secretion increases during gestation
41
As an endocrine organ, the placenta produces what hormones?
estrogens progestins chorionic gonadotropin placental lactogen relaxin
42
What hormone is the basis for pregnancy tests?
chorionic gonadotropin (hCG)
43
How does the kidney act as an endocrine organ?
produces: renin 1,25-dihydroxycholecalciferol erythropoietin
44
How does the pineal gland act as an endocrine organ?
secretes melatonin
45
How do autocoids perform endocrine functions?
many different cells produce cytokines, interleukins and growth factors, that act on themselves
46
Describe how the RAS system regulates blood pressure & electrolyte metabolism.
* **renin** is produced in the juxtaglomerular (**JG**) cells * **JG** cells are sensitive to **blood presure** changes & changes in **Na+ and Cl- concentration** in renal tubular fluid * **renin** is synthesized as **preprorenin** * acts on **angiotensiongen** (produced in the liver) to produce **angiotensin-I** * **ACE** (in the lungs, endothelial cells & plasma) converts **angiotensin-I** to **angiotensin-II** * **angiotensin-II** is a potent **vasoconstrictor** & stimulator of **aldosterone** production
47
What is the biological response of RAS stimulation?
Na+ retention volume expansion increased blood pressure
48
What tissue are able to produce angiotensin-II for local use?
* heart * fat * adrenal cortex * testis * ovary * pineal gland
49
What is 1,25(OH)2 Cholecalciferol & why is it considered a hormone?
active vitamin-D3 it is produce in the body & transported int eh blood-stream to produce effects in target cells
50
Describe the steps involved with producing active vitamin-D3.
* **Vitamin-D3** (cholecalciferol) is produced in the skin from **7-dehydrocholesterol** via sunlight * It is converted to **25-hydroxycholecalciferol** (calcidol), in the **liver** * In the **proximal tubules of the kidney**, **calcidol** is converted to **1,25-dihydroxycholecalciferol** (calcitriol) by **1 alpha-hydroxylase** (mitochondrial enzyme)
51
1,25-dihydroxycolecalciferol acts via what type of receptors?
active vitamin-D3 nucleus recptors
52
What is the function of active Vitamin-D3?
increase Ca2+ absorption fromt he intestine Ca2+ reabsorption in the kidneys
53
What is the name of vitamin-D deficiency in children? In adults?
Children: rickets Adults: osteomalacia
54
What is the body's response when an individual is bled or becomes hypoxic? What hormone regulates these changes?
hemoglobin synthesis enhanced production and release red blood cells from bone marrow are increased **erythropoietin**
55
What type of hormone is erythropoietin? It's levels are markedly increased in what condition?
circulating glycoprotein anemia
56
Where is erythropoietin produced? Its production can be stimulated by what exogenous substances?
endothelial cells of hte peritubular capillaries in the renal cortex (85% kidney, 15% liver) cobalt salts and androgens
57
Recombinant erythropoietin is used in the treatment of what disease?
anemia
58
Where is the pineal gland located? What hormone does it secrete?
posterior region of the epithalamus melatonin
59
What does the pineal gland do?
timing device to keep internal events synchronizd (circadian rhythm) with light-dark cycle of the environment
60
How is melatonin involved with regulating sleep & wake cycles?
* **Light** striking the **retina** generates a signal that is conveyed to the **pineal gland** * stimulation of light **decreases** the amount of **melatonin** produced * During **darkness,** there is an **increase** in **melatonin** synthesis * **N-acetyltransferase** & **adenosylmethionine** activity are increased
61
In addition to regulating the circadian rhythm, what is another beneficial feature of melatonin?
inhibits breast cancer cell growth
62
Prostaglandins are all formed through what reaction?
oxygenation of arachidonic or other C20 fatty acid
63
What is the function of epidermal growth factor?
stimulat growth of many epidermla and epithelial cells
64
What is the function of fibroblast growth factors?
promote proliferation of many different cells
65
What is the function of nerve growth factor?
stimulates growth of mesenchymal and glial cells
66
What is the function of transforming growthfactor-alfa?
stimulates growth of many epidermal and epithelial cells
67
What is the function of transforming growth factor-beta?
exerts both stimulatory and inhibitoryeffects on certain cells
68
How does secretory activity of endocrine glands change with aging?
wanes especially secretion of growth hormones & sex hormones
69
Reduction in growth hormone leads to what changes?
loss of weight & body mass
70
Decrease in DHEA and DHEAS levels leads to what?
aging & cancer
71
What are the side effects of hormone replacement therapy?
heart attack, cancer, breast cancer | (deadlier than the loss of the hormone)
72
What hormones drastically decrease in post-menopausal women? What are the biologiclal effects of this reduction? What were the side effects of hormone replacement therapy?
estrogen and progesterone hot flahes, night sweats, sleep disturances, osteoporosis, depression, vaginal dryness HRT: breast cancer
73
What hormones drastically decrease in older males? What are the biologiclal effects of this reduction? What were the side effects of hormone replacement therapy?
androgens (T and DHT) brittle bone, lack of muscle mass, lack of strength, depression Testosterone supplement: heart attack GH supplement: cancer DHEA supplement: no clinically significant effect

S3B2 Biochemistry (9 decks)

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