1. MEN: feedback loop

2. WOMEN: Menstrual cycle (no fertilization)

3. WOMEN: Hormones of the menstrual cycle

4. WOMEN: Feedback loop of the early and mid
follicular phases

5. WOMEN: Late
follicular phase LH surge

6. POSITIVE FEEDBACK NEGATIVE FEEDBACK Stimulatory Inhibitory Positive
GnRH
Negative
feedback
GnRH 2 2 3
(LH) 3
Anterior
pituitary LH 1
Anterior
pituitary 1
Estrogen
Progesterone 4
Ovary
Ovary
Before ovulation
After ovulation
1. During the menstrual cycle, before ovulation, small amounts of estrogen are secreted from the ovary.
2. Estrogen stimulates the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus and luteinizing hormone (LH) from the anterior pituitary.
3. GnRH also stimulates the release of LH from the anterior pituitary.
4. LH causes the release of additional estrogen from the ovary. The GnRH and LH levels in the blood increase because of this positive-feedback effect.
1. During the menstrual cycle, after ovulation, the ovary begins to secrete progesterone in response to LH.
2. Progesterone inhibits the release of GnRH from the hypothalamus and LH from the anterior pituitary.
3. Decreased GnRH release from the hypothalamus reduces LH secretion from the anterior pituitary. GnRH and LH levels in the blood decrease because of this negative-feedback effect.

7. DISCUSSION OF ENDOMETRIOSIS ARTICLE