Sex Hormones Flashcards
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?
- Steroid hormones that stimulate male physical and reproductive characteristics
- Testosterone is the primary biological androgen
- Mainly synthesised and released by the testes and the adrenal gland
- Can be converted into oestrogen
What are Oestrogens?
- Steroid hormones that function as the primary female reproductive hormones
- In non-pregnant women the primary naturally occuring oestrogen is oestradiol
- 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.