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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
Q

Where is androgen-binding protein produced?

Its production is stimulated by what signals?

What is its function?

A

Sertoli cells

stimulated by testosterone and FSH

locatd within testes to maintain high concentration of total androgens

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26
Q

Describe regulation of testosteone secretion from the hypothalamus to spermatogenesis.

A
  • 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

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27
Q

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?

A

folicle

17beta-estrdiol

FSH

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28
Q

How do peripheral female tissue produce estrogens?

A

from androgens

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29
Q

Describe regulation of estrogen secretion from the hypothalamus to ovulation.

A
  • They hypothalamus secretes GnRH
  • GnRH stimulates the anterior pituitary to secrete FSH and LH
    • FSH stimulates follicle development in the ovary
    • LH stimulates ovulation

This is an example of a negative feedback loop

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30
Q

What hormone is the startign material for estrogen?

A

testosterone

31
Q

Describe what is happens during menstruation in the following tisues

Pituitaty level

Ovary level

Endometrial level

A
  • 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
Q

What is the proposed cause of PMS?

What are the symptom?

It affects what percent of people with uteruses?

A

drop in estrogen & progesterone levels the week before a period

headaches, mood swings, other physical and emotional changes

85% of women

33
Q

What is PMS called when it dirupts work of personal relationships?

A

premenstrual dysphoric disorder (PMDD)

34
Q

Sex hormones bind to proteins produced in what organ?

Describe the percent of androgens and estogens bound to various proteins in the blood?

A

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
Q

Where is the main site of steroid excretion?

How does it occur?

A

liver

steroid ring structure is not broke

Conjugation: glucuronidation & sulfation

36
Q

Identify the type of horomone & the function:

estrogens

A

steroids

maintenance of pregnancy

37
Q

Identify the type of horomone & the function:

progestins

A

steroids

mimic action of progesterone

38
Q

Identify the type of horomone & the function:

chorionic gonandotropin

A

2 subunits (alpha & beta)

activity similar to LH

39
Q

Identify the type of horomone & the function:

placental lactogen

A

protein

acts like prolactin and GH

40
Q

Identify the type of horomone & the function:

relaxin

A

2 proteins

produced in ovarian corpus luteum, inhibits myometrial contractions, secretion increases during gestation

41
Q

As an endocrine organ, the placenta produces what hormones?

A

estrogens

progestins

chorionic gonadotropin

placental lactogen

relaxin

42
Q

What hormone is the basis for pregnancy tests?

A

chorionic gonadotropin (hCG)

43
Q

How does the kidney act as an endocrine organ?

A

produces:

renin

1,25-dihydroxycholecalciferol

erythropoietin

44
Q

How does the pineal gland act as an endocrine organ?

A

secretes melatonin

45
Q

How do autocoids perform endocrine functions?

A

many different cells produce cytokines, interleukins and growth factors, that act on themselves

46
Q

Describe how the RAS system regulates blood pressure & electrolyte metabolism.

A
  • 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
Q

What is the biological response of RAS stimulation?

A

Na+ retention

volume expansion

increased blood pressure

48
Q

What tissue are able to produce angiotensin-II for local use?

A
  • heart
  • fat
  • adrenal cortex
  • testis
  • ovary
  • pineal gland
49
Q

What is 1,25(OH)2 Cholecalciferol & why is it considered a hormone?

A

active vitamin-D3

it is produce in the body & transported int eh blood-stream to produce effects in target cells

50
Q

Describe the steps involved with producing active vitamin-D3.

A
  • 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
Q

1,25-dihydroxycolecalciferol acts via what type of receptors?

A

active vitamin-D3

nucleus recptors

52
Q

What is the function of active Vitamin-D3?

A

increase Ca2+ absorption fromt he intestine

Ca2+ reabsorption in the kidneys

53
Q

What is the name of vitamin-D deficiency in children?

In adults?

A

Children: rickets

Adults: osteomalacia

54
Q

What is the body’s response when an individual is bled or becomes hypoxic?

What hormone regulates these changes?

A

hemoglobin synthesis enhanced

production and release red blood cells from bone marrow are increased

erythropoietin

55
Q

What type of hormone is erythropoietin?

It’s levels are markedly increased in what condition?

A

circulating glycoprotein

anemia

56
Q

Where is erythropoietin produced?

Its production can be stimulated by what exogenous substances?

A

endothelial cells of hte peritubular capillaries in the renal cortex

(85% kidney, 15% liver)

cobalt salts and androgens

57
Q

Recombinant erythropoietin is used in the treatment of what disease?

A

anemia

58
Q

Where is the pineal gland located?

What hormone does it secrete?

A

posterior region of the epithalamus

melatonin

59
Q

What does the pineal gland do?

A

timing device to keep internal events synchronizd (circadian rhythm) with light-dark cycle of the environment

60
Q

How is melatonin involved with regulating sleep & wake cycles?

A
  • 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
Q

In addition to regulating the circadian rhythm, what is another beneficial feature of melatonin?

A

inhibits breast cancer cell growth

62
Q

Prostaglandins are all formed through what reaction?

A

oxygenation of arachidonic or other C20 fatty acid

63
Q

What is the function of epidermal growth factor?

A

stimulat growth of many epidermla and epithelial cells

64
Q

What is the function of fibroblast growth factors?

A

promote proliferation of many different cells

65
Q

What is the function of nerve growth factor?

A

stimulates growth of mesenchymal and glial cells

66
Q

What is the function of transforming growthfactor-alfa?

A

stimulates growth of many epidermal and epithelial cells

67
Q

What is the function of transforming growth factor-beta?

A

exerts both stimulatory and inhibitoryeffects on certain cells

68
Q

How does secretory activity of endocrine glands change with aging?

A

wanes

especially secretion of growth hormones & sex hormones

69
Q

Reduction in growth hormone leads to what changes?

A

loss of weight & body mass

70
Q

Decrease in DHEA and DHEAS levels leads to what?

A

aging & cancer

71
Q

What are the side effects of hormone replacement therapy?

A

heart attack, cancer, breast cancer

(deadlier than the loss of the hormone)

72
Q

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?

A

estrogen and progesterone

hot flahes, night sweats, sleep disturances, osteoporosis, depression, vaginal dryness

HRT: breast cancer

73
Q

What hormones drastically decrease in older males?

What are the biologiclal effects of this reduction?

What were the side effects of hormone replacement therapy?

A

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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