Sex Hormones

Question 1

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?

Answer 1

Androgens + Oestrogens

Question 2

What are Androgens?

Answer 2

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

Question 3

What are Oestrogens?

Answer 3

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

Question 4

what are the different reproductive organs between the sexes

Answer 4

Question 5

what is the process of sexual differentiation into males?

Answer 5

Question 6

what is the male phenotype and female phenotype

Answer 6

XY and XX

Question 7

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?

Answer 7

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

Question 8

what is the process of sexual differentiation into Females?

Answer 8

Question 9

what are the pubertal changes

Answer 9

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

Question 10

What scale is used to define the stages of puperty?

Answer 10

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.

Question 11

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

Answer 11

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!

Question 12

where are androgens released from in the adrenal glands

Answer 12

zona reticularis in the adrenal cortex

Question 13

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

What happens to them?

Answer 13

Weak androgens

• DHEA
• DHEA-sulphate
• Androstenedione

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

Question 14

androgens released from testes are responsible for

Answer 14

facial hair (high levels needed)

Question 15

describe the HPG axis activity before puberty?

Answer 15

• low levels of GnRH, FSH and LH
• Ovarier/Testes release low levels of sex steroids
• Axis is not stimulated enough to release eggs/sperm

Question 16

describe the HPG activity after puberty

Answer 16

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

Question 17

what are kiss peptins?

Answer 17

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)

Question 18

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

Answer 18

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.

Question 19

increased testosterone released from the growing testes drives…

Answer 19

formation of secondary sexual characteristics deep voice, facial hair

Question 20

What are some causes of irregular menstrual cycles?

Answer 20

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

Question 21

where in the Hypothalamus is GnRH released from?

Answer 21

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

Question 22

Where is LH and FSH released from?

Answer 22

gonadotroph cells in anterior pituitary in regular pulses

Question 23

state the anatomy of the testes

Answer 23

comprised of seminiferous tubules and leydig cells

Question 24

Outline the HPG axis for males

Answer 24

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.

Question 25

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

Answer 25

Sertoli cells - found in **seminiferous tubules** of the testes

Question 26

What is the main precursor of testosterone?

Answer 26

Pregenolone

Question 27

main effects of Testosterone?

Answer 27

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

Question 28

Where does spermatogenesis occur?

Answer 28

Seminiferous tubules

Question 29

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

Answer 29

**Spermatogonial stem cells:** • Sperm production **Sertoli cells** * Secretes supporting fluid into lumen * Nutrition * Protection * Regulation * forms blood-testes barrier

Question 30

when does spermatogenesis occur?

Answer 30

starts at puberty

Question 31

Outline the process of spermatogenesis

Answer 31

**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

Question 32

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

Answer 32

not motile in seminiferous tubules gain motility when non-motile sperm transported to **epididymis** where they are stored and gain motility

Question 33

how is the blood-testis barrier

Answer 33

**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.

Question 34

prolactin role

Answer 34

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

Question 35

What happens in sperm capacitation?

Answer 35

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

Question 36

what is the acrosome reaction? what is oocyte activation?

Answer 36

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

Question 37

what Non-Hormonal factors can affect testosterone levels?

Answer 37

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

Question 38

what is klinefelter syndrome

Answer 38

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.

Question 39

what is hyperprolactinaemia and what causes it?

Answer 39

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.

Question 40

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

Answer 40

4-8 weeks

Question 41

what are primary oocytes?

Answer 41

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**

Question 42

Outline the 5 stages of the Menstrual Cycle

Answer 42

**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.

Question 43

what happens during fertilisation?

Answer 43

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)

Question 44

what is Blastocyst

Answer 44

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)

Question 45

Implantation

Answer 45

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.