14.3 Hormonal Regulation of the Reproductive System

key hormones of reproductive system

• gonadotropin releasing hormone (GnRH)

• follicle stimulating hormone (FSH)

• luteinizing hormone (LH)

• estrogen

• progesterone

• testosterone

• inhibin

GnRH production site

hypothalamus

GnRH target organ

anterior pituitary

GnRH function in male reproductive system

stimulates release of FSH and LH

GnRH function in female reproductive system

stimulates release of FSH and LH

FSH production site

anterior pituitary

FSH target organs

testes and ovaries

FSH function in male reproductive system

stimulates development of sex organs and sperm production (seminiferous tubes)

FSH function in female reproductive system

stimulates development of follicles in ovary and egg production

LH production site

anterior pituitary

LH target organs

ovaries and testes

LH function in male RS

stimulates production of testosterone in intersitial cells

LH function in female RS

triggers ovulation and stimulates estrogen production (with FSH)

estrogen production site

ovary (follicles)

estrogen target organ

entire body

estrogen function in female RS

stimulates development of female reproductive tract and secondary sex characteristics

progesterone production site

ovary (corpus luteum)

progesterone target organ

uterus

progesterone function in female RS

causes urerine thickening; when low, flow stage begins

testosterone production site

testes (intersitial cells)

testosterone target organ

entire body

testosterone function in male RS

stimulates production of male reproductive tract and secondary sex characteristics

inhibin production site

testes (Sertoli cells)

inhibin target organs

anterior pituitary and hypothalamus

inhibin function in both male and female reproductive systems

inhibit FSH and LH production

chromosomal (XX, XY) sex

genetic sex determined at fertilization

testis determining factor (TDF)

gene carried by Y chromosome in males which triggers the production of androgens

androgens

male sex hormones; initiates development of male sex organs in fetus

puberty

period in which reproductive system completed its development and becomes fully functional

andropause

the gradual decline in testosterone levels as males age. includes symptoms: depression, fatigue, loss of muscle/bone mass, decreased libido and sperm amount

menstrual cycle

monthly cycle where endometrial lining prepares for pregnancy

stages of menstrual cycle

1. flow stage

2. follicular phase

3. ovulatory phase

4. luteal phase

flow stage days 1-5

low levels of estrogen/progesterone stimulate endometrium lining to be shed via uterine contractions. high FSH begins follicular phase

follicular stage (days 6-13)

follicles develop, estrogen is secreted and endometrium begins to restore. LH secretions increase (more estrogen/progesterone)

ovulatory phase (day 14)

LH spike causes ovulation, secondary oocyte bursts from ovary

luteal phase (days 15-28)

corpus luteum secretes progesterone and some estrogen, endometrial lining thickens in preparation of pregancy. if no pregancy, corpus luteum degenerates due to lack of LH causing E and P levels to drop.

menopause

few follicles remain and ovulation stops — end of reproductive life. includes symptoms: mood swings, increased cholesterol, decreased bone mass and increased risk of urerine/breast cancer

hormone replacement therapy (HRT)

treatment where individual is given hormones to replace those the body is no longer making (estrogen/testosterone)