Relation of the Hypothalamo-Pituitary-Gonadal System to Decline of Reproductive Functions in Aging Female Rats
In mammalian species, reproductive functions decline w ith aging and the capacity to produce live offspring by the female usually ceases well before death of the individual. Many neuroendocrine and other mechanisms involved in these changes remain to be investigated. In women, menstrual cycles generally cease between 40–50 years of age, but for 2–3 years prior to the menopause, they tend to become irregular and there is an increase in the number of anovulatory cycles (Timeras and Meisami, 1972), suggesting a possible decrease in LH secretion. The ovaries tend to form large or cystic follicles and there is inadequate development and often early involution of the corpus luteum leading to shortening of the cycle. Both estrogen and progesterone secretion appear to decline in women approaching the menopause and the ovaries show a reduced capacity to respond to gonadotropins. In the postmenopausal period, ovulation rarely occurs, the ovariesloose their follicles and become fibrotic, and the pituitary responds to loss of inhibitory gonadal feedback by increasing release of gonadotropins, particularly FSH. However, a sharp fall in gonadotropin release has been observed in women after 80 years of age (Albert et al., 1956).
KeywordsEstrous Cycle Estradiol Benzoate Estradiol Benzoate Ether Stress Irregular Cycle
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