Negative Feedback Control of Gonadotropins in Male Rhesus Monkeys: Effects of Time After Castration and Interactions of Testosterone and Estradiol-17β

Resko, John A.; Quadri, S. K.; Spies, Harold G.

doi:10.1210/endo-101-1-215

Cited by 70 publications

(33 citation statements)

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“…On the basis of suppression of serum gonadotropins and the dose-dependent stimulatory effects on accessory sex gland weights, the need for episodic testosterone secretion is not readily apparent. However, the difference between constant steroid release via Silastic capsules and normal episodic release by the testes should be kept in mind, particularly since Resko et al (1977) were unable to suppress LH and FSH in the castrate male monkey with testosterone capsules alone, whereas Plant et al (1978) were successful when they supplemented capsules with pulsatile (injected) testosterone. In the castrate ram, however, administration of testosterone by Silastic capsules appears to be a suitable method of replacement therapy.…”

Section: Discussionmentioning

confidence: 99%

Testosterone Regulation of Luteinizing Hormone and Follicle Stimulating Hormone Secretion in Young Male Lambs1

Schanbacher¹

1980

Journal of Animal Science

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SummaryPolydimethylsiloxane (Silastic) capsules containing crystalline testosterone were implanted subcutaneously in castrate lambs and evaluated for their ability to (1) provide stable, physiological concentrations of serum testosterone and (2) regulate secretion of LH and FSH. Testosterone was nondectable (<.2 ng/ml) between 12 and 24 weeks of age in the serum of castrate lambs implanted with empty capsules but was increased at those ages in Iambs implanted with 20 cm (1.2 + .1 and .5 +-.1 ng/ml), 60 cm (2.8 + .1 and .9 + .1 ng/ml) and 180 cm (6.6 + .3 and 1.9 + .2 ng/ml) of testosterone-filled Silastic tubing. Serum concentrations of LH and FSH were suppressed by exogenous testosterone and did not exceed concentrations in intact control rams as long as serum testosterone concentrations were greater than 1 ng/ml. In conclusion, simultaneous suppression of serum LH and FSH by concentrations of testosterone that cause a dose-dependent stimulatory effect on accessory sex gland weights indicates that testosterone is a physiological regulator of gonadotropin secretion in ram lambs. Although testosterone per se may not be directly responsible for negative feedback on LH and FSH secretion, the resultsThe author acknowledges the technical assistance of Ms. Becky Weber and Ms. Donna Taubenheim and the cooperation of the Nebraska Agr. Exp. Sta., Univ. of Nebraska, Lincoln. Portions of these data were presented at the 1979 Annu. Meet. of the ASAS. (Schanbacher, 1979)

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Section: Discussionmentioning

confidence: 99%

Testosterone Regulation of Luteinizing Hormone and Follicle Stimulating Hormone Secretion in Young Male Lambs1

Schanbacher¹

1980

Journal of Animal Science

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“…Oestradiol appears to play a key role in the negative feedback control of testosterone. In long-term castrated rhesus monkeys, physiological doses of testosterone do not reduce LH unless a small amount of oestradiol is also given (Resko et al 1977). Also, men with aromatase deficiency or oestrogen resistance show raised LH and follicle-stimulating hormone (see Roselli et al 2001).…”

Section: Where Do Androgens Act In the Brain?mentioning

confidence: 99%

The endocrinology of sexual arousal

Bancroft¹

2005

Journal of Endocrinology

346

197

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The relevance of testosterone, oestradiol and certain peptides (oxytocin (OT), -endorphin and prolactin (PRL)) to sexual arousal in humans is reviewed. In addition to behavioural studies, evidence of distribution of gonadal steroid receptors in the brain and the limited evidence from brain imaging are also considered. Testosterone plays a key role in the adult male, with clear, consistent evidence from studies of hypogonadal and eugonadal men. The roles of testosterone in the development of sexual arousability, and in the aging male, are less clear. The relevance of aromatization and of non-sexual effects of testosterone which might indirectly influence sexual arousal are not well understood. Testosterone in the female presents a more complex, less consistent picture. One possible explanation is a much greater variability across women in responsiveness to testosterone. A 'desensitization hypothesis' to account for the striking gender differences is offered. There is limited evidence of a direct effect of oestradiol on sexual arousability in women. The extent to which testosterone in women acts by conversion to oestradiol or by increase of free oestradiol is not yet clear. The role of peptides in sexual arousal remains uncertain, partly because of the multiple roles and sites of action of most peptides. OT and -endorphin appear to have both excitatory and inhibitory effects. PRL has been proposed as an inhibitory factor via direct inhibition of dopaminergic activity, but the evidence for this is inconclusive. Whereas the traditional concept of 'hormone' continues to apply to the role of testosterone and oestradiol in sexual arousal, peptides present a more complex role.

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“…The negative feedback of testosterone on LH secretion is a well-established physiological system in many mammali an species including man [9,10,27,44,50,51,53,55,56,61,67], It is clear from our study, and other experiments [1,3,46,57], that blood concentrations of testosterone approach ing those found during the night in intact males [3,21,45,49] are necessary in order to initiate the suppression of LH secretion. Lower serum testosterone concentrations are un able to suppress LH levels in castrated monkeys [47,51,58].…”

Section: Discussionmentioning

confidence: 52%

Serum and CSF Concentrations of Testosterone and LH Related to Negative Feedback in Male Rhesus Monkeys

Dubey¹,

Herbert²,

Abbott³

et al. 1984

Neuroendocrinology

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Testosterone and LH concentrations were studied in blood and cerebrospinal fluid (CSF) in 8 adult male rhesus monkeys. All males were initially intact and 7 were subsequently castrated and implanted with an ascending series of testosterone capsules. In 4 of the males, serum testosterone levels were significantly higher at 21.00 h than at 09.00 h when the monkeys were intact. Following castration of these 4 males, 4–10 testosterone capsules produced serum concentrations similar to those previously found at 09.00 h; levels equivalent to those at 21.00 h were attained with 12–14 capsules. The proportion of unbound testosterone in serum represented 2% of total serum concentrations, but increased to 4% at high serum concentrations (12–14 capsules). In contrast, the proportion of unbound testosterone in CSF represented 100% of CSF levels. The levels of testosterone in CSF remained at values equal to 2–3% of total serum concentrations throughout the study. The levels of unbound serum testosterone and testosterone levels in the CSF were similar throughout the study in 3 of the 4 monkeys. In the fourth animal, supraphysiological serum testosterone levels occurred with 12 and 14 implants, and, at this time, the level of testosterone in CSF was less than the concentrations of unbound testosterone in serum. Following an intravenous bolus injection of testosterone, the steroid rapidly entered CSF when either 6 or 14 capsules were in place. Although the clearance of testosterone was similar within either compartment during both treatments, the half-life of testosterone in CSF was significantly shorter than in serum at high serum concentrations (14 capsules). Serum and CSF LH levels rose rapidly after castration, reaching maximal levels 8–12 days later with CSF LH levels consistently representing 2–3% of serum concentrations. Post-castration LH concentrations did not change until nocturnal testosterone levels were reached (12–14 capsules), when LH levels were suppressed in both serum and CSF. Subsequent reduction of serum testosterone levels (to 6 capsules) maintained the low LH concentrations. Seemingly, high testosterone concentrations in either serum or CSF, equivalent to nocturnal levels in intact males, were required to initiate LH suppression, but not to maintain it.

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Negative Feedback Control of Gonadotropins in Male Rhesus Monkeys: Effects of Time After Castration and Interactions of Testosterone and Estradiol-17β

Cited by 70 publications

References 0 publications

Testosterone Regulation of Luteinizing Hormone and Follicle Stimulating Hormone Secretion in Young Male Lambs1

Testosterone Regulation of Luteinizing Hormone and Follicle Stimulating Hormone Secretion in Young Male Lambs1

The endocrinology of sexual arousal

Serum and CSF Concentrations of Testosterone and LH Related to Negative Feedback in Male Rhesus Monkeys

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