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Human Development > Reproductive endocrinology + menstrual cycle > Flashcards

Reproductive endocrinology + menstrual cycle Flashcards

1
Q

where are the following hormones produced:
*GnRH
*FSH
*LH

A

GnRH= (Gonadotrophin-releasing hormone) is produced in the arcuate nucleus(ARC) of mediobasal hypothalamus; GnRH then travels down to anterior pituitary gland.

The anterior pituitary gland produces FSH and LH (both are glycoproteins). FSH, LH, GnRH travel down to gonads.

n.b. half-life of LH is 30 min, whereas halflife of FSH is several hours

GnRH, FSH and LH all synthesised from cholestrol (27C); all hyrdophobic and can bypass cell membrane + get into cytoplasm+nucleus

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2
Q

what is a gonad

A

Gonads are glands that produce hormones that are involved in reproduction (testes or ovaries)

Gonads produce testosterone, oestrogen and progesterone

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3
Q

where and what is cortisol hormone produced from

A

Cortisol is a hormone synthesised from cholestrol and produced by the two adrenal glands, which are located on top of each kidney. The pituitary gland in the brain regulates cortisol production. Cortisol plays an important role in the stress response

n.b. cortisol is NOT a sex hormone

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4
Q

what is the function of GnRH

A

GnRH{Gonadotrophin-releasing hormone} is responsible for stimulating the synthesis and the release of both LH and FSH

GnRH= (Gonadotrophin-releasing hormone) is produced in the arcuate nucleus(ARC) of mediobasal hypothalamus; GnRH then travels down to pituitary gland.

GnRH will travel down hypophyseal portal system into pituitary gland where it acts on gonadotrophs/ gonadotrophin cells which are the endocrine cells that produce LH + FSH

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5
Q

what is the function of prolactin

A

prolactin (198 amino acid polypeptide for milk production) is synthesised by lactorophs in anterior pituitary gland. Travel down to breast tissue

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6
Q

oxytocin in made and released where? what is its function in labour?

A

Oxytocin is produced in the hypothalamus and is secreted into the bloodstream by the posterior pituitary gland.

Oxytocin stimulates positive feedback loop in labour to increase uterine contraction (myometrium contraction) (continues a little after birth to prevent blood clots; however birth of the baby is the signal for +ve feedback to end)

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7
Q

where is TSH synthesised and released from

A

TSH (Thyroid-stimulating hormone) is a glycoprotein hormone produced by the anterior pituitary. It is the primary stimulus for thyroid hormone production by the thyroid gland

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8
Q

what is the intermediate precursor responsible for all sex hormones from cholestrol

A

cholestrol–> pregnenolone {is the intermediate precursor} for
*progesterone (ketone w 21C)
*oestrogen
*DHEA (dehydroepiandrosterone)

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9
Q

what are the different types of Oestrogen and when are they most predominant

A

*Oestradiol (E2 or 17-beta) predominant during reproductive years (ages 12-51)

*Oestriol (E3)
predominant during pregnancy
*Oesterol (E4) only produced in pregnancy and conveys protection against breast cancer

*Oestrone (E1)
predominant during menopause

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10
Q

where are the following steroids produced in females vs males?
*testosterone
*dihydrotestosterone (DHT)
*progesterone
*oestradiol

A

testosterone:
males= leydig cells (testes)
females= thecal cells (ovary=25%, adrenal=25%, and peripheral conversion in adipose tissue 50%)

DHT: (most potent/active form of testosterone; key role in sexual development in men)
males= made from testosterone by 5alpha-reductase in Sertoli cells (testes) + prostate gland
females= peripheral conversion from testosterone

Progesterone:
males=adrenal glands (in men progesterone is an intermediate to testosterone)
females= corpus luteum (ovary), syncytiotrophoblasts (placenta), adrenals as an intermediate

Oestradiol
males= (n.b. its Estradiol 17β (E2) in men) peripheral tissues and delivered via plasma (oestradiol conversion from testosterone; depends on presence of aromatase) + some is synthesised in leydig cells of testicular intersitium
females= granulosa cells (ovary), peripheral conversion from testosterone,and syncytiotrophoblasts (in placenta)

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11
Q

what are androgens and what are their functions in males and females

A

Androgens are sex hormones that bring on puberty. They help your body mature and boost your sex drive

functions of androgens in both sex:
- promote protein anabolism, somatic growth, muscle development + ossification= increase bone density
- enter puberty
- RBCs
- sexual desire + function
- influence aggressive behaviour
- induce body hair (in females= pubic + axillary)
- regulate gonadotrophin secretion

functions in females:
-regulates menstruation
-aids conception + pregnancy
-minimises bone loss (osteoporosis)

function in males:
-regulates male reproductive system differentiation + fertility
-induce male secondary sexual characteristics
-support spermatogenesis

N.B. IN WEEK 7 OF PREGANCY SRY (SEX DETERMINING REGION Y GENE) causes initiation and development of TESTICLES

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12
Q

In Sertoli cells, which enzyme converts testosterone to DHT (dihydrotestosterone)

A

5alpha-reductase converts testosterone to DHT (dihydrotestosterone)

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13
Q

Describe steroid synthesis of spermatocytes in males

think of sertoli cells as the ‘nursing cells’ for sperm

A

*GnRH (gonadotrophin releasing hormone) is released from arcuate nucleus (ARC) of mediobasal hypothalamus and travels dowmn to pituitary. GnRH causes the release of LH + FSH by anterior pituitary.

LH stimulates testosterone production by Leydig cells
Main target of testosterone + pituitary FSH are Sertoli cells

FSH stimulates Sertoli cells to produce enzyme 5alpha-reductase converts testosterone to DHT

Sertoli cells then secrete androgen binding protein (ABP)

ABP binds to steroid hormones e.g. testosterone {so ABP makes it less lipophillic) and carries it to seminiferous tubule to the developing spermatocytes and spermatids= SPERMATOGENESIS

primary spermatocyte then divides meiotically (Meiosis I) into two secondary spermatocytes; each secondary spermatocyte divides into two equal haploid spermatids by Meiosis II. The spermatids are transformed into spermatozoa (sperm) by the process of spermiogenesis

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14
Q

Spermatogenesis is strongly and continuously stimulated by FSH and LH; where are the receptors for each of these?

A

LH has receptor at Leydig cells
-produce androgen (testosterone + DHT)
-weak spermatogenesis

FSH has receptors on Sertoli cells
-weak spermatogenesis
-increases expression of androgen nuclear receptors

BOTH HORMONES STIMULATE THE PRODUCTION OF ANDROGENS= so if one missing huge effect as they all work together to make the androgens in males

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15
Q

in males, what hormone inhibits pituitary release of FSH and hypothalamic release of GnRH

what is the function of this same hormone in females

A

in males, inhibin B a glycoprotein produced by Sertoli cells when sperm count is high to inhibit pituitary release of FSH and hypothalamic release of GnRH = INHBITIS SPERMATOGENESIS

in females, inhibin B glycoprotein is produced by granulosa cells exerts negative control on FSH production during menstrual cycle

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16
Q

steroid synthesis in females

A
  1. LH released from anterior pituitary gland
  2. Stimulates testosterone production by Theca cells
  3. Testosterone enters granulosa cells
  4. Converted to oestrogen by aromatase
  5. Oestradiol stimulates formation of LH receptors on granulosa cells
  6. Allows follicle to respond to LH
    =Ovulation
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17
Q

function of oestrogen in males

A

oestrogen in males:
-testicular leydig and sertoli cells synthesise oestrogen
-most oestrogen in blood comes from aromatisation of testosterone in peripheral organs

in both genders:
-norm bone growth + development
-regulates gonadotropin release
-regulates glucose + fat metabolism

18
Q

function of oestrogen in females

A

oestrogen= primarily produced during follicular phase in ovaries, corpus luteum, and in syncytiotrophoblasts in placenta- a small but significant amount also produced in liver, heart, skin and brain

-stimulates growth of mammary glands + endometrium (uterus lining)
-induces female secondary sexual characteristics
-prepare uterus for spermatozoa transport
-increase vascular permeability
-regulates gonadotrophin (FSH,LH,hCG) secretion

19
Q

function of progestogens (all the progesterone derivatives) in males

A

in males progesterone is made in adrenal glands (progesterone is an intermediate to testosterone)

FUNCTION OF PROGESTOGENS IN MALES:
- regulates spermatogenesis, sperm capacitation/acrosome reaction + testosterone biosynthesis in leydig cells
in both sexes progestogens;
- regulates gonadortophin release
- sleep improvement + inhibits CNS tumours
- stimulates weight gain + apetite

20
Q

function of progestogens (all the progesterone derivatives) in females

A

*mainly produced in luteal phase from the corpus luteum= progesterone is preparing the endometrium for implantation during ‘secretory phase’ (ovulation/juicy phase) of menstrual cycle

*progestogens effect cervix, vagina and breast(mammary gland enlargement) for implantation of ferilised egg; if implantation takes place then placental progesterone maintains endometrium in pregnancy

21
Q

what hormone stimulates apetite

A

PROGESTERONE (or derivates of it; progestogens) stimulates apetite= weight gain

Progesterone is released in high levels at luteal phase (most likely cycle time to gain weight)

22
Q

what is a new drug that is a naturally occuring antidepressant for postpartum depression + how does it work

A

allopregnanolone (ALLO)= is a progesterone metabolite (i.e. synthesised from progesterone)

n.b. decreased GABA function accompanies depressed or manic mood states

med is solution:
ALLO is a positive allosteric modulator of the GABA-A inhibitory receptor in CNS
*promotes normal sleep
*reduces anxiety
*reduces depression

23
Q

what is the function of relaxin in females vs males

A

females: relaxin is secreted by corpus luteum + placenta
- late stage pregnancy; relaxin softens pubic symphysis + ligaments around pelvis to prepare for labour

males: relaxin secreted by prostate gland; found in seminal fluid to enhance sperm motility

24
Q

steroid synthesis in men

A
  • Gonadotrophin releasing hormone is released by the arcuate nucleus of mediobasal hypothalamus it then travels down to pituitary
  • Causes release of FSH and LH by the anterior pituitary
  • LH:
    o Stimulates testosterone by Leydig cells
  • FSH (and Testosterone):
    o Stimulates Sertoli cells to release the enzyme 5a reductase
     Testosterone to DHT
     Sertolli cells secrete androgen binding protein and tubular fluid
     ABP binds to testosterone and carries it to the seminiferous tubule
     Spermatogenesis
25
Q

What is the structure of steroids?

A
  • Lipid structure based on cholesterol
  • 27 carbon skeleton in 4 rings
26
Q

Where are the following hormones produced?

*androstenedione
*Dihydroepiandrosterone (DHEA)

A

androstenedione= made in Testes (leydig cells) and adrenal gland (intermediate)

DHEA= made in Testes (leydig cells) and adrenal gland

27
Q

What is required to synthesis hormones?

A

Oxidative enzymes in the mitochondria and ER

First step is Cholesterol to pregnenolone (intermediate precursor to all sex hormones)

28
Q

What are the 3 main classes of steroids?

A

Progestagens
Androgens
Oestrogens

29
Q

What do Oestrogens do?

A
  • Stimulates growth of mammary gland and endometrium
  • Induces female secondary sexual characteristics
  • Prepares uterus for spermatozoa transport
  • Increases vascular permeability
  • Regulates gonadotophin secretion
30
Q

What is the order of potency of the oestrogens (most potent to least)

A

Oestradiol (E2)= predominant during reproductive years (12-51)
(think diol like die cuz young ppl wanna die)

Oestriol (E3)= predmoninant during pregnancy (think -ol like lol cuz pregannt)

Oestrone (E1)= predominant during menopause (strone= strong like menopausal women)

31
Q

What do androgens (testrosterone,DHT) do in men?

+ What does it do in men and women?

A

Maintain male somatic tissue differentiation
Induce male secondary sexual characteristics
Supports spermatogenesis

In men and women:
Influences sexual and aggressive behaviour
Promotes protein anabolism and growth
Regulates gonadotrophin secretion for testosterone.
Induces body hair

32
Q

What is the order of potency of androgens? (most potent to least)

A

DHT
Testosterone
Androstenedione
DHEA

33
Q

What do progestogens do?

A

o Luteal progesterone prepares endometrium for implantation
o Placental progesterone maintains the endometrium in pregnancy.

34
Q

How do steroid receptors work?

A
  • Steroid hormone binds to receptor in nuclear membrane
  • Binds to hormone receptor complex in nucleus
  • Influences transcription and therefore protein export.
35
Q

What are the actions of LH and FSH

A
  • LH surge triggers ovulation and converts follicle into corpus luteum
  • Supports theca cells in ovary and acts on leydig cell in the testes
  • Maintains luteal function
  • FSH stimulates growth of immature graafian follicles
  • Enhances production of androgen binding protein
36
Q

What gonadotropin is secreted by the placenta?

A

hCG (syncytiotrophoblast)
Maintains corpus luteum in pregnancy

37
Q

What is the structure of gonadotrophins?

A
  • Made up of a and b glycol protein subunits.
  • A is subunit identical in FSH , LH and HcG
  • B subunit is difference in each
  • B subunits are same sequence of amino acids in LH and hCG but hCG has 24 more
38
Q

What does Activin do?

A

Increase FSH activity and enhances LH action in Men and women

39
Q

what is FSH aromatization?

A

FSH stimulates granulosa cells in the ovarian follicles to synthesize aromatase, which converts androgens produced by the thecal cells to estradiol.

40
Q

What are prostaglandins and what is their effect?

A
  • Lipid component derived from fatty acids
  • Effects include muscle contraction (uterine contractions), vasodilation, medication of inflammation, hormone regulation, cell growth control and temperature regulation
41
Q

What does PGF2a do?

A

Prostaglandin F2a= In utero activates mechanical events of parturition(giving birth) including contraction and cervical ripening.

PGF2A increases the intracellular calcium concentration by stimulating the release of stored calcium, which produces a phasic contraction that permits blood flow to the foetus between contractions and optimises the ability of the uterus to expel the foetus

42
Q

what layer of the endometrium is the one ‘shed’ during menstruation

A

stratum functionalis (innermost layer of endometrium)

the other layer {stratum basalis} is NOT shed

Human Development (8 decks)

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