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Flashcards in Sex Hormones Deck (46)
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The many physical changes seen during development and puberty that lead to sexual differentiation are primarily caused by two groups of steroid hormones. What are they?

Androgens + Oestrogens


What are Androgens?

  1. Steroid hormones that stimulate male physical and reproductive characteristics
  2. Testosterone is the primary biological androgen
  3. Mainly synthesised and released by the testes and the adrenal gland
  4. Can be converted into oestrogen


What are Oestrogens?

  1. Steroid hormones that function as the primary female reproductive hormones
  2. In non-pregnant women the primary naturally occuring oestrogen is oestradiol
  3. Synthesised from androgens and released by the ovaries


what are the different reproductive organs between the sexes


what is the process of sexual differentiation into males?


what is the male phenotype and female phenotype

XY and XX


XY in a male cannot cross over like a matching chromosome pair. What is different about the Y chromosome and what signals the production of the male characteristics?

Non pairing and pairing region is made on Y Chromosome. The non pairing region has the sry gene activation of this gene results in primordial gonads being formed


what is the process of sexual differentiation into Females?


what are the pubertal changes

1) Adolescent growth spurt • involving skeleton, muscle and viscera
2) Sex specific increases in growth rate • leads to phenotypic sexual dimorphism
3) Changes in body composition • particularly muscle and fat
4) The development of reproductive function • gonadal activity, secondary sexual characteristics


What scale is used to define the stages of puperty?

The Tanner scale
A 1-5 scale of physical development

5 stages of physical development are defined, based on measurements of external primary and secondary sex characteristics such as breast development, genital development and pubic hair.


What are the two events that cause an increase in reproductive hormones and pubertal changes.

Adrenarche: Increased secretion of Androgens from adrenal gland. This is a process of early sexual maturation

Then following this is the inceased HPG axis activity: increased hormone secretions from ovaries/testes  


these two events are independent!


where are androgens released from in the adrenal glands

zona reticularis in the adrenal cortex


What do the adrenal glands release during adrenarche and name some examples?

What happens to them?

Weak androgens

  • DHEA
  • DHEA-sulphate
  • Androstenedione


They are then converted peripherally in the body to stronger androgens - testosterone and dihydrotestosterone which results pubertal changes


androgens released from testes are responsible for

facial hair (high levels needed)




describe the HPG axis activity before puberty?

- low levels of GnRH, FSH and LH

- Ovarier/Testes release low levels of sex steroids

- Axis is not stimulated enough to release eggs/sperm


describe the HPG activity after puberty

  • Hypothalamus releases - GnRH   
  • Anterior Pituitary - releases FSH and LH 
  • Ovary/Testis - releases egg or sperm and oestrogen and testosterone


what are kiss peptins?

a family of peptides encoded by the kiss-1-gene that control the ontset of puberty

It is a g-protein coupled receptor ligand for GPR54 . Mutation of GPR54 - hypogonadotrophic hypogonadism (lack of reprodutive function)




What is LH and FSH? What do they do and where are they released?

Released from the Anterior Pituitary Glands, Stimulated by GnRH.

LH - Luteinising Hormone

in Males: Stimulates production of testosterone in testes

In Females: controls the reproductive cycle and ovulation. stimulates oestrogen

FSH - Follicule Stimulating Hormone

In males: Stimulates the growth and maturation of the testes and spermatogenesis

in Females: stimulates the growth and maturation of ovarian follicles.


increased testosterone released from the growing testes drives...

formation of secondary sexual characteristics deep voice, facial hair 


What are some causes of irregular menstrual cycles?

Anovulatory (ain't no ovulation)
Missing luteal phase
Variable oestrogen levels from developing follicles


where in the Hypothalamus is GnRH released from?

The preoptic area in the hypothalamus releases GnRH into the pituitry gland via  the median eminence in regular pulses


Where is LH and FSH released from?

gonadotroph cells in anterior pituitary in regular pulses


state the anatomy of the testes

comprised of seminiferous tubules and leydig cells


Outline the HPG axis for males

Leydig cells stimulated by LH which secrete testosterone

Setroli cells are stimulated by FSH which secrete androgen-binding globulin which binds to testosterone making it less lipophilic to stimulate spermatogenesis. It concentrates testosterone in the lumen increasing fertility They also secrete inhibin which signals to the HPG axis to decrease sperm production.


What cells do FSH stimulate in the males and where are they found?

Sertoli cells - found in seminiferous tubules of the testes


What is the main precursor of testosterone?



main effects of Testosterone?

• Male hormone - anabolic
• Primary and secondary sexual characters
• Libido and sexual behaviour
• Stimulates spermatogenesis


Where does spermatogenesis occur?

Seminiferous tubules


What cells are found in the Seminiferous tubules and what are their roles?

Spermatogonial stem cells:

• Sperm production

Sertoli cells

  • Secretes supporting fluid into lumen
  • Nutrition 
  • Protection 
  • Regulation
  • forms blood-testes barrier


when does spermatogenesis occur?

starts at puberty


Outline the process of spermatogenesis

Golgi phase

  • The golgi apparatus creates a vesicle of enzymes around the nucleus.
  • Mitochondria start to move to the other side of the cell.
  • The centriole starts to form an axoneme, the cytoskeletal core of the tail.

Cap phase

  • Spermatid DNA is condensed in the nucleus.
  • The golgi apparatus surrounds the nucleus and the enzyme vesicle forming the acrosomal cap

Acrosome phase

  • The axoneme extends to become the tail of the sperm.
  • Temporary cytoskeleton structures called manchettes support the growing tail.

Maturation phase

  • Excess cytoplasm is phagocytosed by Sertoli cells to produce mature sperm


What part of the reproductive system are sperm not motile in, and in which part to they gain motility

not motile in seminiferous tubules

gain motility when non-motile sperm transported to epididymis where they are stored and gain motility


how is the blood-testis barrier

Tight junctions between serteoli cells forms a barrier between blood and lumen of seminiferous tubules. allows sertoli cells to control the environment within the lumen.


prolactin role

released from the pituitary and increases LH receptor expression on leydig cells, which increases testosterone release.


What happens in sperm capacitation?

Takes place in the uterus

Switching on of sperm via increased calcium influx causing increased intracellular cAMP levels- increased motility

Cholesterol and gycoproteins are removed from the sperm cell surface by enzymes such as heparin in the uterus


what is the acrosome reaction? what is oocyte activation?

triggered by contact of sperm with oocyte

Interaction with zona pellucida 3 protein (ZP3) on oocyte membrane prevents cross-species fertilisaition and cortical granules are relased that makes the oocyte impereable to other sperm

Acrosome releases hyaluronidase and acrosin enzymes break though egg coating allowing fertilisation


what  Non-Hormonal factors can affect testosterone levels?

• Environment
• Climate (heat)
• Radiation
• Air pollution
• Food chain pollution
• Stress


what is klinefelter syndrome

  1. A genetic disorder in which a male with X and Y chromosomes also has an additional X chromosome.
  2. Individuals will have 47 chromosomes instead of the normal 46 with XXY.
  3. Effects vary between individuals, many people will not show any symptoms, but it can result in hypogonadism and reduced fertility.


what is hyperprolactinaemia and what causes it?

Abnormally high levels of circulating prolactin which inhibits GnRH.
Can be caused by pituitary tumours.

Also often a side-effect of various prescription drugs that affect dopamine.


at what week of foetal development does foetal development start to occur?

4-8 weeks


what are primary oocytes?

  1. Diploid cells with 46 chromosomes.
  2. Start meiosis, but stop at prophase I.
  3. Become dormant, halted at this stage of development.

At birth, no further oocytes can be generated


Outline the 5 stages of the Menstrual Cycle

Menstrual phase (day 1-5)
Uterine lining sloughs off and is removed from the body.
Once the uterine lining is removed the endometrium starts to proliferate again.

Proliferative phase (day 5-13)
Endometrium, the lining of the uterus, begins to proliferate and thicken, tubular glands and arteries form.
Stimulation of progesterone receptors synthesis in endometrial cells.

Late-Proliferative phase (day 13-14)
The glands are long and tortuous due to active growth. Stroma is gradually becoming oedematous.

Secretory phase (day 15-22)
The growing endometrium becomes dependant on progesterone released from the corpus luteum.
Enlargement of tubular glands which begin secreting mucus and glycogen in preparation for implantation of the fertilized ovum.

Late-secretory phase (day 23-28)
If fertilization does not occur, the corpus luteum degenerates, progesterone levels fall and the endometrium degenerates.
Uterine glands are wide. Arteries begin contracting and capillary beds begin leaking blood into the endometrium and uterus.



what happens during fertilisation?

Secondary oocyte is fertilised by sperm cell

Polar body and zygote (46 chromosomes) is formed

 Polar body degenerates.


The zygote starts to divide as it travels along the fallopian tube towards the uterus (8 cells within it)


what is Blastocyst

formed after 5 days Zygote

Wihin the blastocyst, there are 3 components:

1. inner cell mass (that will become the embryo),

2. blastocoele (fluid space)


3. trophoblast (surrounds the inner cell mass and will become the placenta)




The trophoblast layer (that will become placenta) attaches to the surface of the endometrium.

The blastocyst invades the endometrium.

Trophoblast cells release human chorionic gonadotropin which maintains the corpus luteum during early pregnancy. This is to ensure appropriate progesterone release so the endometrial lining can grow.