Extra- and Intracellular Effects of Divergent Selection for Pituitary Responsiveness to Gonadotropin-Releasing Hormone in Prepubertal Ram Lambs1

Evans, Neil P.; Bramley, T. A.; McNeilly, J. R.; Webb, Robert I.

doi:10.1095/biolreprod57.1.128

Cited by 3 publications

(2 citation statements)

References 54 publications

(75 reference statements)

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“…Whether the mechanism mediating this increase relates to an increase in LH synthesis or an increased GNRH receptor expression remains to be investigated. Evidence to date has supported the hypothesis that GNRH has the ability to upregulate its own receptor (Katt et al 1985, Turzillo et al 1995a, 1995b, Sakurai et al 1997 and that the amount of LH released is a function of the GNRH receptor number (Evans et al 1997) and LH content (Clarke et al 1987). It should be recognized that these findings do not exclude any additional contribution stemming from increased GNRH input.…”

Section: Discussionmentioning

confidence: 97%

Pituitary and testis responsiveness of young male sheep exposed to testosterone excess during fetal development

Recabarren¹,

Rojas-García²,

Einspanier³

et al. 2013

Reproduction

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Prenatal exposure to excess testosterone induces reproductive disturbances in both female and male sheep. In females, it alters the hypothalamus-pituitary-ovarian axis. In males, prenatal testosterone excess reduces sperm count and motility. Focusing on males, this study tested whether pituitary LH responsiveness to GNRH is increased in prenatal testosterone-exposed males and whether testicular function is compromised in the testosterone-exposed males. Control males (nZ6) and males born to ewes exposed to twice weekly injections of 30 mg testosterone propionate from days 30 to 90 and of 40 mg testosterone propionate from days 90 to 120 of gestation (nZ6) were studied at 20 and 30 weeks of age. Pituitary and testicular responsiveness was tested by administering a GNRH analog (leuprolide acetate). To complement the analyses, the mRNA expression of LH receptor (LHR) and that of steroidogenic enzymes were determined in testicular tissue. Basal LH and testosterone concentrations were higher in the testosterone-exposed-males. While LH response to the GNRH analog was higher in the testosterone-exposed males than in the control males, testosterone responses did not differ between the treatment groups. The testosterone:LH ratio was higher in the control males than in the testosterone-exposed males of 30 weeks of age, suggestive of reduced Leydig cell sensitivity to LH in the testosterone-exposed males. The expression of LHR mRNA was lower in the testosterone-exposed males, but the mRNA expression of steroidogenic enzymes did not differ between the groups. These findings indicate that prenatal testosterone excess has opposing effects at the pituitary and testicular levels, namely increased pituitary sensitivity to GNRH at the level of pituitary and decreased sensitivity of the testes to LH.

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Section: Discussionmentioning

confidence: 97%

Pituitary and testis responsiveness of young male sheep exposed to testosterone excess during fetal development

Recabarren¹,

Rojas-García²,

Einspanier³

et al. 2013

Reproduction

View full text Add to dashboard Cite

show abstract

“…These areas, especially in sexually dimorphic regions such as the chin, cheeks, sternum, upper abdomen, and upper back, are highly sensitive to even slight elevations above this range, which can stimulate further hair growth [42,43]. In cases where estrogen doses, adequate for feminization, prove insufficient for complete androgen suppression, the use of an antiandrogen becomes imperative for favorable clinical outcomes [44,45]. Antiandrogens can be categorized into three groups: those that interfere with androgen-receptor signaling, those that limit the conversion of testosterone to its potent metabolite, dihydrotestosterone (DHT), and those that reduce androgen production [46].…”

Section: The Role Of Gender-affirming Hormonal Therapy (Gaht)mentioning

confidence: 99%

Exploring Hormone Therapy Effects on Reproduction and Health in Transgender Individuals

Moustakli,

Tsonis

2023

Medicina

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Transgender individuals often face elevated mental health challenges due to gender dysphoria, but gender-affirming treatments such as surgery and hormone therapy have been linked to significant improvements in mental well-being. The potential influence of time and circadian rhythms on these treatments is prevalent. The intricate interplay between hormones, clock genes, and fertility is profound, acknowledging the complexity of reproductive health in transgender individuals. Furthermore, risks associated with gender-affirming hormonal therapy and potential complications of puberty suppression emphasize the importance of ongoing surveillance for these patients and the need of fertility preservation and family-building options for transgender individuals. This narrative review delves into the intricate landscape of hormone therapy for transgender individuals, shedding light on its impact on bone, cardiovascular, and overall health. It explores how hormone therapy affects bone maintenance and cardiovascular risk factors, outlining the complex interplay of testosterone and estrogen. It also underscores the necessity for further research, especially regarding the long-term effects of transgender hormones. This project emphasizes the critical role of healthcare providers, particularly obstetricians and gynecologists, in providing affirming care, calling for comprehensive understanding and integration of transgender treatments. This review will contribute to a better understanding of the impact of hormone therapy on reproductive health and overall well-being in transgender individuals. It will provide valuable insights for healthcare providers, policymakers, and transgender individuals themselves, informing decision-making regarding hormone therapy and fertility preservation options. Additionally, by identifying research gaps, this review will guide future studies to address the evolving healthcare needs of transgender individuals. This project represents a critical step toward addressing the complex healthcare needs of this population. By synthesizing existing knowledge and highlighting areas for further investigation, this review aims to improve the quality of care and support provided to transgender individuals, ultimately enhancing their reproductive health and overall well-being.

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Pituitary responsiveness to diurnal and nocturnal GnRH pulses in melatonin-treated ewe lambs

Recabarren

Lobos²,

Cendoyya³

et al. 2000

Reprod. Fertil. Dev.

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It has been shown that oral administration of melatonin to Suffolk ewe lambs, from 10 weeks of age onwards, advances the onset of puberty compared with control lambs maintained under the same natural photoperiod. Luteinizing hormone (LH) pulse frequency at 20 and 26 weeks of age was unchanged by melatonin. However, LH pulse amplitudes greater than 1 ng mL(-1) were consistently observed in melatonin-treated lambs, suggesting either a high responsiveness of the pituitary gland to endogenous gonadotrophin-releasing hormone (GnRH) pulses, or a large amount of GnRH released by each pulse. The purpose of the present study was to assess the pituitary responsiveness to six diurnal and six nocturnal exogenous pulses of GnRH (10 ng kg(-1) bodyweight) in melatonin-treated ewe lambs (3 mg melatonin daily at 1600 hours, from 10 weeks of age; n = 5) and control lambs of the same age (n = 5), born in the spring and kept under natural photoperiod. Pulses of GnRH were given intravenously at 60-min intervals by means of an indwelling jugular catheter from 0900 to 1400 hours and from 2100 to 0200 hours to ewe lambs of 20 and 26 weeks of age. Blood samples were collected at 10-min intervals using a contralateral jugular vein catheter from 1 h before and up to 1 h after the last GnRH pulse. The difference (delta) between plasma LH concentrations at 0 min and the greatest concentration of LH after each GnRH pulse was calculated and compared in the same group. The total area under the GnRH response curve (AUC) was also calculated and compared within and between the groups. The AUC of melatonin-treated lambs (66.1 +/- 5.94 and 52.24 +/- 7.42 ng mL(-1)/6 h, diurnal and nocturnal respectively) was greater than that of control lambs (39.42 +/- 4.29 and 32.82 +/- 3.6 ng mL(-1)/6 h diurnal and nocturnal respectively; P<0.05) at 20 weeks of age. At 26 weeks of age, only the diurnal total AUC was greater in melatonin-treated lambs than in control lambs (60.17 +/- 7.98 and 29.8 +/- 5.02 ng mL(-1)/6 h respectively; P<0.05). Delta LH concentrations in response to the first diurnal pulse of GnRH were greater than those in response to the fifth diurnal GnRH pulse (P<0.05) in melatonin-treated lambs of 20 weeks of age. Also, the delta LH concentrations in response to the first three diurnal GnRH pulses were greater than to the last three nocturnal pulses of GnRH (P<0.05). Delta LH concentrations were greater in response to the second diurnal pulse of GnRH than to the last three diurnal GnRH pulses, and greater than the responses to the first and the last four nocturnal GnRH pulses (P<0.05), at 26 weeks of age in melatonin-treated lambs. The response to nocturnal pulses of GnRH was similar. In control lambs, the responses to diurnal and nocturnal GnRH pulses were similar at 20 and 26 weeks of age. These results suggest that melatonin enhances the pituitary responsiveness to GnRH pulses in ewe lambs.

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Extra- and Intracellular Effects of Divergent Selection for Pituitary Responsiveness to Gonadotropin-Releasing Hormone in Prepubertal Ram Lambs1

Cited by 3 publications

References 54 publications

Pituitary and testis responsiveness of young male sheep exposed to testosterone excess during fetal development

Pituitary and testis responsiveness of young male sheep exposed to testosterone excess during fetal development

Exploring Hormone Therapy Effects on Reproduction and Health in Transgender Individuals

Pituitary responsiveness to diurnal and nocturnal GnRH pulses in melatonin-treated ewe lambs

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