Abstract
It is well known that the reproductive system is one of the first biological systems to show age-related decline. While depletion of ovarian follicles clearly relates to the end of reproductive function in females, evidence is accumulating that a hypothalamic defect is critical in the transition from cyclicity to acyclicity. This minireview attempts to present a concise review on aging of the female reproductive neuroendocrine axis and provide thought-provoking analysis and insights into potential future directions for this field. Evidence will be reviewed, which shows that a defect in pulsatile and surge gonadotropin hormone-releasing hormone (GnRH) secretion exists in normal cycling middle-aged female rats, which is thought to explain the significantly attenuated pulsatile and surge luteinizing hormone (LH) secretion at middle-age. Evidence is also presented, which supports the age-related defect in GnRH secretion as being due to a reduced activation of GnRH neurons. Along these lines, stimulation of GnRH secretion by the major excitatory transmitter glutamate is shown to be significantly attenuated in middle-aged proestrous rats. Corresponding age-related defects in other major excitatory regulatory factors, such as catecholamines, neuropeptide Y, and astrocytes, have also been demonstrated. Age-related changes in hypothalamic concentrations of neurotransmitter receptors, steroid receptors, and circulating steroid hormone levels are also reviewed, and discussion is presented on the complex interrelationships of the hypothalamus-pituitary-ovarian (HPO) axis during aging, with attention to how a defect in one level of the axis can induce defects in other levels, and thereby potentiate the dysfunction of the entire HPO axis.
Original language | English (US) |
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Pages (from-to) | 273-283 |
Number of pages | 11 |
Journal | Steroids |
Volume | 70 |
Issue number | 4 |
DOIs | |
State | Published - Apr 2005 |
Keywords
- Aging
- Estrogen
- Estrous cycle
- Follicle-stimulating hormone
- Gonadotropin hormone-releasing hormone
- Hypothalamus
- Luteinizing hormone
- Neuroendocrine
- Ovulation
- Pituitary
- Progesterone
- Reproduction
- Steroid
ASJC Scopus subject areas
- Biochemistry
- Molecular Biology
- Endocrinology
- Pharmacology
- Clinical Biochemistry
- Organic Chemistry