The Hormones

GnRH = gonadotropin-releasing hormone

FSH = Folicle-stimulating hormone

LH = Luteinizing hormone

Testosterone

Estrogen

Progesterone

Female Hormones and reproductionSite of production Hormone Main function

Hypothalamus(to anterior pituitary)

GnRH

Anterior pituitary FSH Stimulates folliclegrowth, secretion ofestrogen,

Anterior pituitary LH Stimulates ovulation,growth of corpusluteum, and secretion ofestrogen andprogesterone

Ovaries Estrogren Female secondarycharacteristics,maturation of eggs,growth of uterine lining

Ovaries Progesterone Stimulates growth ofuterine lining andplacenta formation

Hormonal control of spermatogenesis:

Immature males don’t produce sperm

At puberty the hypothalamus produces GnRH

This stimulates the anterior pituitary to produce LH & FSH

LH stimulates testosterone production which along with FSH stimulates the spermatogenesis.

Testosterone also stimulates secondary sex characteristics

In males•Facial hair• Deepening of the voice•Growth of skeleton•Sweat gland development (acne)•Enlargement of penis

In femalesBreast developmentHair growth

The Menstrual Cycle:

Hypothalamus releases GnRH

GnRh stimulates release of FSH & LH by pituitary

FSH & LH stimulate development of follicles

Follicles secrete estrogen

2 follicles form per month

Increased growth of follicle releases more estrogen

Estrogen has 3 effects

•Promotes further growth of follicle, oocyte

•Stimulates growth of endometrium in uterus

•Stimulate increase in FSH & LH

The surge in LH has three effects

•Trigger meiosis I in oocyte

•Final explosive growth of follicle & ovulation

•Turns remnants of follicle into corpus luteum

Corpus luteum secretes estrogen & progesterone

These inhibit the pituitary & hypothalamus thus stopping FSH & LH

This stops formation of further follicles

Stimulates further growth of endometrium

What happens next depends on…..

….if fertilization occurs or not.

If pregnancy does not occur then….

the corpus luteum disintegrates after 1 week after ovulation

This is because progesterone stops LH production which stimulates corpus luteum growth.

Without the corpus luteum, progesterone and estrogen levels drop which causes the endometrium to die.

It is shed as menstrual flow that begins about the 27th or 28th day.

The reduced level of progesterone means that the hypothalamus and pituitary can start producing GnRH

The cycle starts again.

If pregnancy does occur then …..

The embryo itself starts secreting a LH like hormone called CG or chorionic gonadotropin that prevents the breakdown of the corpus luteum.

Which continues to produce progesterone and estrogen which nourishes the endometrium and the embryo.

The embryo releases so much CG that it comes out in the urine and can be used as a pregnancy test.

Birth Control pills contain estrogen and progesterone which suppresses LH which is the hormone that triggers ovulation

Efforts are being made to develop a male pill which will suppress the production of FSH which causes spermatogenesis and continue LH production so that testosterone production.

This means a man would be infertile, but not impotent.