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08:02
Fecal Glucocorticoid Analysis: Non-invasive Adrenal Monitoring in Equids
Published on: April 25, 2016
A glucocorticoid sensitive biphasic rhythm of testosterone secretion
Journal of Neuroendocrinology
|July 16, 2009
Summary
The study reveals that while the hypothalamic-pituitary-testicular (HPT) axis rhythm is not dependent on the hypothalamic-pituitary-adrenal (HPA) axis, elevated glucocorticoids disrupt testosterone secretion patterns in rats.
Area of Science:
- Endocrinology
- Chronobiology
- Neuroendocrinology
Background:
- The hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-testicular (HPT) axes exhibit reciprocal interactions.
- Stress impacts testosterone secretion, and rats display a diurnal testosterone rhythm, unlike humans.
Purpose of the Study:
- To investigate the circadian pattern of testosterone secretion in rats under basal conditions.
- To determine how circulating corticosteroid levels influence the HPT axis rhythm.
Main Methods:
- Utilized an automated blood sampling system for precise measurement of plasma testosterone and corticosterone.
- Administered methylprednisolone and performed adrenalectomy in rats to manipulate HPA axis activity.
Main Results:
- Identified a bimodal circadian pattern of basal testosterone secretion in rats, with episodes approximately 12.6 hours apart.
- Observed that the circadian rise in corticosterone levels coincided with a nadir between testosterone secretory episodes.
- Methylprednisolone treatment abolished the bimodal testosterone rhythm, while adrenalectomy preserved it.
Conclusions:
- The endogenous circadian rhythm of testosterone secretion is independent of normal HPA axis function.
- Elevated glucocorticoid levels can abolish the normal rhythmicity of the HPT axis.
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