HL 1 Biology

6.6a Female Hormones


Human reproduction: fusion of a sperm (from male) with an egg (from female)

<<Female Reproductive System>>

Gene tdfwhen present in genome, babies develop as males

  • usually located on Y chromosome
  • if embryo has 2 X chromosomes = no copy of tdf present
  • without tdf  => embryonic gonads develop ovaries (no testosterone)

Estrogen & progesterone: the 2 female hormones always present in pregnancy

  • secreted first by the mother’s ovaries and later by placenta
  • with absence of testosterone & presence of estrogen + progesterone = female genitalia develop

<<Menstrual Cycle>>

Menstrual cycle: the sequence of events in which females produce egg and thicken the endometrium for reproduction

<<Hormonal Control of Menstrual Cycle>>

  1. Group of follicles (a fluid filled sac) +  oocytes (eggs) within them are stimulated to grow
  2. Endometrium is thickening; while follicles are developing
  3. Most developed follicle breaks open & releases an egg into the oviduct (becomes a body corpus luteum)
  4. Other follicles degenerate
  5. corpus luteum breaks down if fertilization doesn’t occur, then thickening of endometrium breaks down to be shed during menstruation

<<Hormone Levels During Menstrual Cycle>>

Hormones levels measured in mass per militre

  • actual masses very small = progestrone. FSH, LH are measured in nanograms (ng) and estrogen in picograms (pg)
  • First half of menstrual cycle: folliclar phase
  • Second half of cycle: luteal phase, as a corpus luteum develops in the ovary
  • the endometrium breaks down and is released during menstruation (thickens again for preparation of implantation of an embryo)


The Female Athlete Triad (p. 272)

1 a) As the number of menstrual cycles is greater than 10, there is a significant increase in bone. Thus, the more menstrual cycles taken place, the higher the value of the bone mineral diversity. The overall effect on the bone density however does not contrast to the bone. 

b) The neck of the femur has a very low density during the 4-10 cycle yet on the other hand, the trochanter has a higher density while the 11-13 cycles. Both of the situations represent how more cycles of menstruation apparent result to higher bone mineral density.

2 a) Runners have higher bone density than the mean because they could have a better diet or could have a average speed of running method, causing the bone density to be higher.

b) Lower bone density than the mean can be present because the runners may be lacking nutrient intake or because of the faulty representation of the older runners. Also, the runners may have a low estrogen level, causing the bone density to be lower than average. Consumption of high energies could also effect the bone density to be lower.

3 a) Female athletes have few or no menstrual cycles because of the reduction in estrogen, which causes the menstrual cycle to slow down. Another reason includes, saving resources in order to stay with the moderate running methods.

b)Eating disorders and low body weight in female athletes could include the performance of reducing consumption of food and decreasing the amount of exercise.

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