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. 2014 Dec 31;2014:153127. doi: 10.1155/2014/153127

Table 1.

Stages of ovarian aging in a female rat as described by Lu et al. (1979) [24].

Age (months) Stages of ovarian aging in female rats
5 months Reproductive maturity
(i) Estrous cycle (4-5 days)
(ii) Elevated and constant levels of estradiol
(iii) Low levels of progesterone
(iv) Lack of hormone surges and ovulation

6–8 months Ovarian decline
(i) Decreased levels of estradiol and progesterone
(ii) Little or no follicles

10–12 months Irregularity of estrous cycles

19 months Constant estrous cycle
(i) Low to medium levels of serum estradiol, estrone, testosterone, androstenedione, and progesterone
(ii) Very low levels of 20α-hydroxyprogesterone
(iii) No preovulatory release of gonadotropin and prolactin
(iv) Increased levels of FSH

24 months Prolactin
(i) Increased levels of prolactin (abolished by ovariectomy)
(ii) Retained ability to develop follicles and corpora
(iii) Retained ability to secrete steroid hormones