Chapter 19

Gonadal Hormones

Objectives

• Define each of the Key Terms• Discuss the hormonal regulation of the female menstrual cycle• Discuss the utilization of hormones in pregnancy testing

Key Terms

• Amenorrhea• Androgen• Corpus luteum• Follicular phase• Luteal phase• Ovulation• GHR• FSH• LH• Progesterone• Estriol• Estradiol• Ovaries

• Follicle• HCG• Placenta• Anterior pituitary gland• Hypothalamus gland• Ectopic pregnancy• Fallopian tubes• Testes• Endometrium• Estrogens

• HCG ( Human corionic gonadotropin )

– Hormone synthesized by the placenta– HCG detection is the basis for serum / urine pregnancy tests

– Similar structure as FSH and LH – HCG stimulates progesterone production by the corpus luteum

– HCG concentrations highest in the 1st trimester– Detectable 1-2 days after conception

– HCG is decreased in ectopic pregnancies and spontaneous abortions ( miscarriages )

– HCG is elevated in multiple fetus’ and gonadal tumors

HCG concentrations during pregnancy

• FEMALE REPRODUCTIVE ENDOCRINOLOGY

– Principle hormones

• FSH ( Follicle Stimulating Hormone )• LH ( Lutenizing Hormone )• Progesterone• Estrogens ( Estradiol , Estrone, Estriol )

– Three phases of the menstrual cycle

• Follicular Phase: FSH and LH Development of a follicle(fluid filled sac housing the egg)

• Ovulation: LH surge and release of the egg from the follicle

• Luteal Phase: Corpus Luteum ( formed from the empty follicle ) secretes progesterone to build the endometrium ( lining of the uterus) in preparation for implantation

• Follicular ( Day 1 of menstruation )

– FSH stimulates ovarian follicle ( layer around ovum )– Follicle produces estradiol – Estradiol stimulates development of endometrium– Follicle matures for 14 days

• Ovulation ( Day 14 )

– LH surge by anterior pituitary causes follicle to release ovum

• Luteal ( After ovulation )

– Follicle changes into the corpus luteum– Corpus luteum synthesizes estrogens ( estradiol + estrone )– Estrogens stimulate uterus, fallopian tubes, vagina, breast and fat

development– LH stimulates corpus luteum to synthesize progesterone– Progesterone stimulates uterus and breast

• Two different things can happen !

• Fertilization

– The placenta produces HCG

– HCG stimulates progesterone synthesis by the coupus luteum

– Continued progesterone secretion by the corpus luteum supports the health of the uterus and the placenta

– The pregnancy continues

• No fertilization

– No placenta No HCG No progesterone + estrogens

– Corpus luteum breaks down and progesterone synthesis stops

– Endometrial lining of the uterus breaks down ( menstruation )

• How do birth control pills work?

– Birth control pills take advantage of the normal cyclic feedback mechanism of the hypothalamic -- pituitary -- ovarian cycle. Constant dosages of estrogen and progesterone, in amounts and patterns similar to those occurring during pregnancy, inhibit fertilization. This mimics pregnancy, when there is also an absence of the characteristic rise and fall of hormones, and no egg is released.

• How do birth control pills work?

– Birth control pills take advantage of the normal cyclic feedback mechanism of the hypothalamic -- pituitary -- ovarian cycle. Constant dosages of estrogen and progesterone, in amounts and patterns similar to those occurring during pregnancy, inhibit fertilization. This mimics pregnancy, when there is also an absence of the characteristic rise and fall of hormones, and no egg is released.

• LH and FSH in men

– LH stimulates the testes to produce testosterone and estradiol

– Testosterone promotes secondary male sexual characteristics

– LH and FSH stimulate spermatogenesis

LH and FSH help to keep Charles Atlas a“manly man.”

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