Reproduction Hormones - 05

Hormonal Regulation - Males

At puberty, hypothalmus increases GnRH production

• GnRH acts on anterior pituitary - causes LH and FSH to be released

• LH stimulates Leydig cells (interstitial cells) to secrete testosterone

  • Stimulates sperm production, controls reproductive system structures

• FSH stimulates Sertoli cells to secrete molecules required for spermatogenes (sperm releasage)

Overabudance of testosterone inhibits GnRH and LH secretions (negative feedback) and stimulates cells to produce inhibin

• Inhibin, FSH production

Hormonal Regulation - Females

At puberty. GnRH production increases

• Causes Ant, Pituitary to release FSH and LH

  • FSH and LH act on ovaries to produce estrogen and progesterone - Control menstrual cycle

• Menstrual cycle = Ovarian cycle + uterine cycle

Ovarian Cycle - Part 1

Stage 1 - Follicular Phase

• FSH from the Ant. Pituitary stimlates ovarian follicles to mature

• The developing follicle secretes estrogen (and small amount of progesterone)

• Estrogen causes the endometrium to thicken and repair

• Rising estrogen lvls stimulates hypothalmus to release GnRH

• GnRH causes surge in LH triggers ovulation

  • Mature follicle ruptures and releases the ovum

OVarian Cycle - Part 2

Stage - Luteal Stage

• LH causes ruptured follicle to become the corpus luteum

  • Secretes: Progesterone, Some estrogen, Inhibin

• Progesterone causes endometrium thickening and inhibits LH

• Inhibit inhibits FSH secretion

  • Helps prevent uterine contractions

*If fertilization does not occur:

• Corpus Luteum degenerates

• Progesterone, estrogen, and inhibin lvls drop

• Endometrium is shed (menstruation begins

• FSH secretion rises again, starting a new cycle

Female reproductive hormone control

Estrogen

• dual role

  • Negative feedback loop (low lvl estrogen = inhibit LH and FSH)

  • Positive feedback (high lvl of estrogen = release for LH and FSH)

Once progesterone lvls decrease this leads to endometrium to be shed; menstruation

Menopause

Occurs around 46-54

• Ovarian follicles run out