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Cortisol Reduces Gonadotropin-Releasing Hormone Pulse Frequency in Follicular Phase Ewes: Influence of Ovarian Steroids
- Source :
- Monash University
- Publication Year :
- 2008
- Publisher :
- The Endocrine Society, 2008.
-
Abstract
- Stress-like elevations in plasma glucocorticoids suppress gonadotropin secretion and can disrupt ovarian cyclicity. In sheep, cortisol acts at the pituitary to reduce responsiveness to GnRH but does not affect GnRH pulse frequency in the absence of ovarian hormones. However, in ewes during the follicular phase of the estrous cycle, cortisol reduces LH pulse frequency. To test the hypothesis that cortisol reduces GnRH pulse frequency in the presence of ovarian steroids, the effect of cortisol on GnRH secretion was monitored directly in pituitary portal blood of follicular phase sheep in the presence and absence of a cortisol treatment that elevated plasma cortisol to a level observed during stress. An acute (6 h) cortisol increase in the midfollicular phase did not lower GnRH pulse frequency. However, a more prolonged (27 h) increase in cortisol beginning just before the decrease in progesterone reduced GnRH pulse frequency by 45% and delayed the preovulatory LH surge by 10 h. To determine whether the gonadal steroid milieu of the follicular phase enables cortisol to reduce GnRH pulse frequency, GnRH was monitored in ovariectomized ewes treated with estradiol and progesterone to create an artificial follicular phase. A sustained increment in plasma cortisol reduced GnRH pulse frequency by 70% in this artificial follicular phase, in contrast to the lack of an effect in untreated ovariectomized ewes as seen previously. Thus, a sustained stress-like level of cortisol suppresses GnRH pulse frequency in follicular phase ewes, and this appears to be dependent upon the presence of ovarian steroids. A sustained stress-like level of cortisol reduces GnRH pulse frequency in the follicular phase and appears to require the presence of ovarian steroids.
- Subjects :
- endocrine system
medicine.medical_specialty
Hydrocortisone
media_common.quotation_subject
Gonadotropin-releasing hormone
Article
Gonadotropin-Releasing Hormone
Endocrinology
Internal medicine
Follicular phase
medicine
Animals
Homeostasis
Ovulation
media_common
Estrous cycle
Sheep
Pulse (signal processing)
Chemistry
Ovary
Luteinizing Hormone
Gonadotropin secretion
Kinetics
Follicular Phase
Female
Luteinizing hormone
hormones, hormone substitutes, and hormone antagonists
medicine.drug
Subjects
Details
- ISSN :
- 19457170 and 00137227
- Volume :
- 150
- Database :
- OpenAIRE
- Journal :
- Endocrinology
- Accession number :
- edsair.doi.dedup.....16ed5cf45f9e4e04231528d5ca9c6a78