Fertility Flashcards
What are the 2 gonadotrophic hormones secreted by the pituitary gland?
FSH and LH
What does FSH do in males and females?
Males: testes to produce sperm via stimulation of sertoli cells
Females: growth of ovarian follicles and causes the ovary to secrete oestrogen
What is the role of LH in males and females?
Males: testes secrete testosterone via leydig cells
Females: ovulation and causes progesterone to be produced by the corpus luteum
How does testosterone act on the anterior pituitary and hypothalamus?
Negative feedback to reduce the production of LH and FSH
Negative feedback on hypothalamus to reduce the production of GnRH
How does oestrogen feedback?
Estrogen below 200 will exert a negative feedback
Oestrogen above 200 will exert a positive feedback of LH and FSH
What is GnRH?
Neuropeptide hormone synthesized and released from the GnHR neurones within the hypothalamus and is released in a pulsatile manner
Describe the relationship between GnRH pulses and release of FSH and LH
Oestrogen contractions above 200 will increase GnRH pulsatility driving the release of LH.
During the early menstrual cycle, GnRH frequency is spaced out so only FSH is released, once the frequency is quicker there will be subsequent release of LH
Explain GnRH during puberty?
Appropriate modulatio nof LH freuqncy is essential for puberty and reproductive function. The onset of pubertal maturation is associated with a steady acceleration in GnRH pusatility with a peak at night
What is considered delayed puberty?
In females, no period by 15
In males, no sign of testicular development by 14
Moderated by the activation of GnRH frequency
What are the 2 cycles of the menstrual cycle?
Follicular / proliferative phase
Luteal / secretory phase
What mediates the follicular phase?
FSH
What mediates the luteal phase?
Corpus luteum and therefore progesterone
What is day 1 of the menstrual cycle?
First day of menstrual bleeding
When is the LH surge and what does it do?
Day 14
Influences the follicle to produce progesterone
As progesterone increases it will shut off the production of LH
What is a follice?
An oocyte surrounded by follicular cells (granulosa and theca cells)
Growth of a follice is an increase in the number of follicular cells and the accumulation of follicular fluid
How does the endometrium change over the menstrual cycle?
Thickens under the influence of oestrogen and becomes a secretory tissue under the influence of progesterone
What receptors are found on theca and granulosa cells?
Theca cells: LH
Granulosa cells: FSH
What occurs in the granulosa and theca cells?
FSH acts on the enzyme aromatase to convert the androgen in oestrogen within the granulosa cell
Cholesterol is converted to androgen in the theca cell
How many oocytes are recruited within each menstrual cycle?
5/6
These will all grow but only the dominant follicle will be selected for ovulation. The dominant oocyte might be the one that is most vascular or has the most FSH receptors
How long after the LH surge does ovulation occur?
Approx. 34-36 hrs
How is the corpus luteum formed?
Following ovulation, release of an oocyte and follicle will convert into corpus luteum (full of cholesterol to produce progesterone).
Within the corpus luteum there are no granulosa and theca cells as under the influence of LH will transfer into luteal cells
What are the roles of oestrogen?
Increase thickness of vaginal wall
Regulate LH surge
Reduce vaginal pH through increase in lactic acid production
Decrease viscosity of cervical mucus to facilitate sperm production
What are the roles of progesterone?
Pro-gestational hormone to maintain pregnancy
Maintains thickness of endometrium
Responsible for infertile thick mucus to prevent sperm transport and help prevent infection
Relax the myometrium
Progesterone withdrawal regulates partition
How is sperm made?
Occurs within the testes
Under control of LH, FSH and testosterone
Entire spermatogenic process takes 70 days
Humans produce 1000 sperm every heart beat
What regulates the gate of sertoli cells?
Tight junctions