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Repro 313 > Steroid Hormones. Lecture Three > Flashcards

Steroid Hormones. Lecture Three Flashcards

1
Q

What are all steroid hormones derived from?

A

Cholesterol

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2
Q

What must a compound contain to be considered a steroid hormone?

A

A PERHYDROCYCLOPENTENOPHENANTHRENE nucleus

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3
Q

How is cholesterol obtained by the body?

A

The body can synthesise cholesterol from acetyl CoA but the favoured route is to obtain in through the diet.

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4
Q

What tissues convert cholesterol into steroid hormones?

A

Adrenal glands
Testis
Ovaries
Adipose tissue

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5
Q

What are steroid producing cells characterised by?

A

Large lipid filled vesicles

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6
Q

In general what is found in a steroid producing cell?

A

Abundance of smooth ER (rough ER produces proteins)

Steroids diffuse across the membranes

Abundant lipid droplets

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7
Q

What does steroid hormone synthesis normally involve?

A
  • Introduction of new OH groups
  • Removal of Carbons
  • Interconversion of O= and OH groups
  • Moving double bonds
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8
Q

Whats the rate limiting step of steroid biosynthesis?

A

The conversion of Cholesterol into Progenolone by cholesterol desmolase.

An important point of regulation (LH and ACTH)

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9
Q

Steroid pathways are arranged how?

A

The enzymes are arranged in a biosynthetic unit.

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10
Q

Since the enzymes are arranged in a biosynthetic unit, what are the implications of this?

A

An enzyme defect can have widespread effects

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11
Q

Where does the biosynthetic unit start?

A

The biosynthetic unit starts in the mitochondrial membrane and proceeds to the smooth ER.

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12
Q

How is progenolone converted to progesterone?

A

Progenolone is converted into progesterone by the 3beta hydroxysteroid dehydrogenase enzyme.

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13
Q

What are the steps in testosterone production from progenolone?

A

Conversion of progenolone into 17 OH progenolone by 17 alpha hydroxylase.

Conversion of 17 oh progenolone into dehydroepi androsterone by 17,20 lyase.

Conversion of dehydroepi androsterone into androstrodione and finally into testosterone.

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14
Q

What can testosterone be converted into?

A

5alpha dihydrotestosterone by 5 alpha reductase.

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15
Q

How are oestrogen’s produced?

A

Either Androsterione can be converted into estrone

or

Testosterone can be converted into estradiol

Both by the enzyme aromatase.

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16
Q

Can oestrogen’s interconvert?

A

Yes, requires the enzyme 17beta hydroxysteroid dehydrogenase

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17
Q

Can steroids be made more soluble?

A

Yes by conjugation to give glucosiduronates or sulphates. However less active and therefore have to be deconjugated to become more active.

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18
Q

The bioavailability of sex hormones is regulated by?

A

SHBG

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19
Q

Describe the affinity of globulins and albumins as carrier proteins:

A

Albumin is low affinity-high capacity binding protein while Globulin is a high affinity-low capacity binding protein.

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20
Q

Variations in hormone levels because of SHBG can lead to what?

A

Low SHBG = Diabetes, hypothyroidism

High SHBG = Pregnancy, Anorexia, Hyperthyroidism.

21
Q

What cells does FSH and LH act on in males?

A

FSH - sertoli cells- gamatogenisis

LH - Leydig cells, testosterone production.

22
Q

What cells does FSH and LH act on in females?

A

FSH and LH act on the ovaries to produce gametes and oestrogen + progesterone.

23
Q

The production of gametes results in what hormone being released too and whats its role?

A

Inhibit, this acts on the hypothalamus and pituitary as negative feedback.

24
Q

How are androgens produced in females?

A

Androstenedione is produced via adipose tissue in women.

25
Q

Whats the normal serum levels of testosterone in males and females?

A

11-40nmol/L males

0.5-2.5nmol/L females

26
Q

What inhibits 5aDHT?

A

Propecia

27
Q

What are the relative potencies of some androgens?

A 
5aDHT = 100%
Testosterone = 50%
Androstenedione = 8%
28
Q

What are the functions of androgens?

A
  • Induce and maintain the differentiation of male tissues
  • Induce and maintain secondary sexual characteristics
  • Spermatogenesis
  • Regulation of Gonadotrophs
29
Q

What do anabolic steroids do?

A

Enhance and mimic androgen properties. Promotes cell division and growth i.e muscle growth.

30
Q

Whats a side effect of anabolic steroids?

A

Anabolic effects in sex linked tissues therefore

  • reduced sexual function
  • male baldness
  • testicular atrophy.
31
Q

What is male pseudohermaphroditism?

A

When progesterone production is no longer regulated and excess sexual hormones are produced leading to receptor desensitisation and down regulation.

32
Q

What do oestrogen’s do?

A

Main role is in development and maintenance of female characteristics and fertility.

33
Q

Where is the main site of oestrogen production in non pregnant women?

A

The granulose cells of the growing follicle. Post ovulation the corpus luteum produces a small amount of estradiol.

34
Q

Where additionally is oestrogen produced?

A

IN the adipose tissue where circulating androstenedione and testosterone are converted to oestrone. Principal source of oestrogen in postmenopausal women and men.

35
Q

What is the relative potencies of oestrogen’s?

A

Estrone- 1%
Estradiol - 100%
Estriol - 10%

36
Q

What is the role of oestrogen’s?

A

Stimulate secondary sex characteristics in females
Endometrial growth
Growth and activity of mammary glands
Regulate the secretion of gonadotrophs.

37
Q

Whats the role of oestrogen on the endometrium?

A

Postovulatory, oestrogen stimulates miotic proliferation and thickening of the endometrium

38
Q

Whats the role of oestrogen on cervical mucous?

A

Estradiol increases mucous secretin

39
Q

Whats the role of oestrogen on the vagina?

A

Stimulates proliferation of vaginal epithelial cells.

40
Q

Whats the role of cervical mucous?

A

At times it is less vicious and aids sperm motility into the cervix.

Other times it is highly viscous and blocks sperm entry.

41
Q

What is ferning?

A

The pattern of dry cervical mucous that indicates it has been exposed to oestrogen but not progesterone.

42
Q

What is spinnbarkeit?

A

The stretchiness of cervical mucous

43
Q

What is progesterone?

A

The major steroidal hormone of the corpus lute and the placenta.

44
Q

What is the serum levels of progesterone?

A

Pre-ovulatory = 4nmol/L
LH surge = 4-10nmol/L
Post ovulation = 25-120nmol/L

45
Q

What is the potency of progesterone?

A

100%

46
Q

What is the role of progesterone on the cervix?

A

Reduces mitotic proliferation
Increased water content and vascularity of the stroma
The endometrium becomes more secretory and stable

47
Q

What is the role of progesterone on cervical mucous?

A

Inhibits cervical mucous secretion

48
Q

What is the role of progesterone on CNS?

A

Elevates core temperature by 0.5celcius

Repro 313 (20 decks)

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