1. Hormones and Reproduction The Hormones GnRH = gonadotropin-releasing hormone FSH = Folicle-stimulating hormone LH = Luteinizing hormone Testosterone Estrogen Progesterone

2. Female Hormones and reproduction

3. 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.

4. 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 females • Breast development • Hair growth

5. 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

6. 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…..

7. ….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.

8. 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.

9. Contraception and Hormones 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.