Androgen and estradiol effects on gonadotropin secretion and response to GnRH in ovariectomized pony mares.
Abstract: In Exp. 1, 16 long-term ovariectomized pony mares were used to determine the effects of treatment with estradiol benzoate (EB) and dihydrotestosterone (DHT) benzoate alone, and in combination, on secretion of follicle stimulating hormone (FSH) and luteinizing hormone (LH) in daily blood samples and after three consecutive injections of gonadotropin releasing hormone (GnRH). Administration of EB alone, or in combination with DHT, every other day for 11 d reduced (P less than .05) concentrations of FSH and increased (P less than .05) concentrations of LH in daily blood samples, and increased (P less than .05) the secretion of both gonadotropins after administration of GnRH. Treatment with DHT alone had no effect (P greater than .10) on LH or FSH concentrations in daily blood samples and no effect on the LH response to exogenous GnRH. There was no interaction (P greater than .10) between DHT and EB treatment for any hormonal characteristic. In Exp. 2, the control mares and mares treated with DHT in Exp. 1 were equally allotted to treatment with vehicle or testosterone propionate (TP) every other day for six injections, and then GnRH was administered as in Exp. 1. Treatment with TP had no effect (P greater than .10) on LH or FSH concentrations in daily blood samples but increased (P less than .05) the FSH response to exogenous GnRH, confirming our findings in previous experiments. It is concluded that the TP-induced stimulation of FSH secretion after exogenous GnRH in ovariectomized mares may involve estrogens produced from aromatization of the injected androgen.(ABSTRACT TRUNCATED AT 250 WORDS)
Publication Date: 1986-06-01 PubMed ID: 3090004DOI: 10.2527/jas1986.6261654xGoogle Scholar: Lookup
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Summary
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This research study investigates the impact of various hormone treatments on the secretion of follicle stimulating hormone (FSH) and luteinizing hormone (LH) in ovariectomized pony mares. The study found that treatment with estradiol benzoate and dihydrotestosterone had differing effects on these hormone levels.
Experiment 1: Estradiol Benzoate and Dihydrotestosterone Treatment
- This experiment utilized 16 long-term ovariectomized pony mares to study the effects of Estradiol Benzoate (EB) and Dihydrotestosterone (DHT) treatments.
- The mares were treated with EB and DHT separately and in combination. The effect on FSH and LH secretions in daily blood samples and post-gonadotropin releasing hormone (GnRH) injections was observed.
- The results showed that administration of EB alone or in combination with DHT reduced FSH concentrations and increased LH concentrations in daily blood samples.
- Additionally, these treatments increased the secretion of both FSH and LH following the administration of GnRH.
- Interestingly, treatment with DHT alone had no significant effect on either FSH or LH concentrations in daily blood samples nor on the LH response to exogenous GnRH.
- There was also no interaction observed between DHT and EB treatments when it came to hormone levels.
Experiment 2: Testosterone Propionate Treatment
- In the second experiment, the control mares and the mares treated with DHT in the first experiment were treated with vehicle or Testosterone Propionate (TP).
- Following six injections, GnRH was administered in the same manner as Experiment 1.
- The results indicated that treatment with TP had no substantial effect on FSH or LH concentrations in daily blood samples. However, it did increase the FSH response to exogenous GnRH, confirming previous experimental findings.
Ramifications of the Study
- The main conclusion from this study is that the TP-induced stimulation of FSH secretion after exogenous GnRH in ovariectomized mares is potentially due to estrogens produced from the aromatization of the injected androgen.
- Ultimately, this research offers valuable insights into how different hormonal treatments impact hormone levels in ovariectomized pony mares.
Cite This Article
APA
Garza F, Thompson DL, St George RL, French DD.
(1986).
Androgen and estradiol effects on gonadotropin secretion and response to GnRH in ovariectomized pony mares.
J Anim Sci, 62(6), 1654-1659.
https://doi.org/10.2527/jas1986.6261654x Publication
Researcher Affiliations
MeSH Terms
- Animals
- Dihydrotestosterone / pharmacology
- Estradiol / pharmacology
- Female
- Follicle Stimulating Hormone / blood
- Follicle Stimulating Hormone / metabolism
- Gonadotropin-Releasing Hormone / administration & dosage
- Gonadotropin-Releasing Hormone / pharmacology
- Horses / physiology
- Luteinizing Hormone / blood
- Luteinizing Hormone / metabolism
- Ovariectomy
Citations
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