Pituitary response to steroid replacement therapy in fertile, subfertile and infertile stallions after castration.
Abstract: Recent studies in our laboratory investigating plasma gonadotrophin concentrations before and after castration indicate that the hypothalamic-pituitary axis is not the original site of dysfunction in stallions with idiopathic infertility. In the present study, fertile, subfertile and infertile stallions were subjected to replacement therapy with oestradiol and testosterone 1 year after castration to investigate hypothalamic-pituitary axis function further. Fertile (n=5), subfertile (n=3) and infertile (n=2) castrated stallions of Light horse breeds, aged 11-23 years, were given either oestradiol cypionate or testosterone propionate for 28 days during the breeding season. Oestradiol cypionate in cottonseed oil (30 mg; 6 mg ml(-1)) was administered i.m. at 2 day intervals starting in May for 28 days. Eight weeks after the last oestradiol cypionate injection, testosterone propionate in vegetable oil (85 mg; 8.5 mg ml(-1)) was administered i.m. at 2 day intervals for 28 days. Heparinized blood samples were taken from the jugular vein three times a week from 3 weeks before the start of oestradiol cypionate treatment until 4 weeks after the last testosterone propionate injection. Saline or 25 microg GnRH in 1 ml saline were administered to the stallions on days 24 and 25, respectively, of the 28 day steroid treatments. Jugular blood samples were collected periodically through a catheter from 60 min before saline or GnRH injection until 420 min after injection. The plasma samples were stored at -20 degrees C until analysed for plasma LH, FSH, oestradiol and testosterone concentrations by validated radioimmunoassay. Exogenous steroid treatment increased plasma oestradiol and testosterone concentrations to concentrations close to normal circulating values (oestradiol: 49 pg ml(-1); testosterone: 1.3 ng ml(-1)) in all the groups. There were no significant differences in plasma LH or FSH concentrations among the groups during any of the treatment periods. Oestradiol treatment significantly increased (P < 0.05) LH concentrations, whereas testosterone treatment decreased LH concentrations, although the difference was not significant. Oestradiol treatment significantly decreased FSH concentrations (P < 0.05), whereas testosterone treatment significantly increased FSH concentrations (P < 0.05). There were no differences in LH and FSH responses to GnRH challenge among the three groups of stallions. In conclusion, the results of the present study indicate that the hypothalamic-pituitary axes in these subfertile and infertile stallions were not the original sites of dysfunction. Further studies at the testicular level are required.
Publication Date: 2000-01-01 PubMed ID: 20681116
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- Journal Article
Summary
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The research investigates the impact of replacement therapy with hormones on fertile, subfertile, and infertile male horses, ultimately finding that the hypothalamic-pituitary axis (the system responsible for hormone regulation) is not the initial point of dysfunction for infertility in these animals.
Background: The Hypothalamic-Pituitary Axis
- The hypothalamic-pituitary axis is a complex set of direct influences and feedback interactions among the hypothalamus (a section of the brain), the pituitary gland, and the adrenal glands. It is responsible for the regulation of crucial body processes such as growth, metabolism, and sexual development.
Objective and Methodology of the Study
- The study’s objective was to expand understanding of subfertility and infertility in stallions by investigating whether the hypothalamic-pituitary axis is the root cause of these issues.
- 10 stallions of light horse breeds, characterized as fertile (5), subfertile (3) and infertile (2), were given either oestradiol cypionate or testosterone propionate for 28 days one year after being castrated.
- The stallions were aged between 11 and 23 years.
The Use of Oestradiol and Testosterone
- The hormones oestradiol and testosterone were used in this study for hormone replacement therapy (HRT) which sought to restore hormonal balance in the horses.
- Oestradiol is a form of estrogen, the primary female sex hormone, while testosterone is the primary male sex hormone.
Sampling and Measurement
- Blood sample analyses were conducted three times a week from 3 weeks before the start of treatment until 4 weeks after the therapy to explore the hormonal levels.
- Blood was drawn from the jugular vein, and hormones, including LH (luteinizing hormone), FSH (follicle-stimulating hormone), oestradiol, and testosterone were gauged and noted.
Key Findings
- The study found that the exogenous steroid treatment increased both oestradiol and testosterone levels in all groups of stallions, nearing the normal circulating values.
- There wasn’t a significant difference in LH or FSH concentration amongst the stallions during the treatment periods.
- Oestradiol treatment saw an increase in LH concentrations and a significant decrease in FSH levels. Conversely, testosterone treatment reduced LH levels and significantly boosted FSH levels.
- No differences were recorded in the LH and FSH responses to a GnRH (gonadotropin-releasing hormone) challenge across the three groups.
Conclusion
- Overall, the research indicates that the hypothalamic-pituitary axes in these stallions are not the original sites of dysfunction leading to subfertility or infertility.
- The findings suggest that further research should be conducted at the testicular level to pinpoint the origins of infertility in stallions.
Cite This Article
APA
Roser JF, Tarleton M, Belanger JM.
(2000).
Pituitary response to steroid replacement therapy in fertile, subfertile and infertile stallions after castration.
J Reprod Fertil Suppl(56), 61-68.
Publication
Researcher Affiliations
- Department of Animal Science, University of California, Davis, CA 95616-8521, USA.
MeSH Terms
- Animals
- Estradiol / administration & dosage
- Estradiol / analogs & derivatives
- Estradiol / pharmacology
- Fertility / physiology
- Gonadal Steroid Hormones / administration & dosage
- Gonadal Steroid Hormones / blood
- Gonadal Steroid Hormones / pharmacology
- Gonadotropin-Releasing Hormone / administration & dosage
- Gonadotropin-Releasing Hormone / pharmacology
- Horse Diseases / metabolism
- Horses
- Hypothalamo-Hypophyseal System / drug effects
- Hypothalamo-Hypophyseal System / physiology
- Infertility, Male / metabolism
- Male
- Orchiectomy / veterinary
- Pituitary Gland / drug effects
- Pituitary Gland / metabolism
- Testosterone / administration & dosage
- Testosterone / pharmacology
Citations
This article has been cited 1 times.- Abad Paskeh MD, Babaei N, Entezari M, Hashemi M, Doosti A. Protective Effects of Coenzyme Q10 Along with Fe(2)O(3) Nanoparticles On Sperm Parameters in Rats with Scrotal Hyperthermia: Effects of CoQ 10 and Fe(2)O(3) Nanoparticles On Sperm Parameters. Galen Med J 2022;11:1-7.
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