Effects of letrozole administration on growth and reproductive performance in Markhoz goat bucklings

Letrozole, an aromatase inhibitor, improves seminal parameters and hormonal profile in aged endangered Markhoz bucks

“…Nevertheless, a report in calves by Berger [25] showed that although oral letrozole being associated with lower estradiol, it does not affect testosterone levels and Sertoli cell number, which might be due to the incomplete absorption of letrozole by the ruminal route and other factors such as age and species. We have previously shown that the Sertoli cell number increased in the testis of the letrozole-injected bucklings [20], as also earlier shown in boars. Sertoli cells, as the main testicular target cell for FSH and testosterone, provide a permissive environment that facilitates differentiation, transformation, and replication of germ cells to spermatozoa is via direct contact [15].…”

“…The major source of aromatase substrate, a prerequisite for estrogen production, has been shown to exist in the testicular tissues, mainly Leydig, Sertoli and germinal cells. In men [ 6 ], rat [ 24 ], and ruminants [ 20 ], estrogen acts as a potent negative feedback modulator on the hypothalamus-pituitary-testicular axis and can alter the GnRH and gonadotropin secretion. In males of these species, decreasing estrogen levels by aromatase inhibitors can stimulate GnRH secretion, which in turn, increases the FSH and LH levels, and simultaneously, these high LH levels stimulate intratesticular testosterone production via the Leydig cells.…”

“…A total of 200 sperm was counted under 1,000× magnification in at least five different microscopic fields. The percentage of sperm that swelled under hypotonic conditions was recorded [ 20 ].…”

“…Letrozole therapy has been proposed as a useful strategy that resulted in improved sperm quality, gonadotropins, and testosterone in aged-roosters [ 17 – 19 ]. In our previous study, we found that letrozole improved hormonal profile, testicular and seminal characteristics during the puberty of Markhoz bucks [ 20 ], but whether this aromatase inhibitor has positive reproductive effects on these endangered goats in older ages remains unknown. Thus, the objectives of present study were to evaluate the effects of letrozole on semen characteristics and hormonal profile in aged Markhoz bucks.…”

Zinc and Shell Flour as Innovative Natural Aromatase Blocker to Increase Testosterone Concentration

“…The types of aromatase blockers used today are diverse, both commercial and natural alternative products. Commercial materials such as letrozole [26] and Zn are derived from shells [27] Zinc is either the macromineral that serves to increase the concentration of testosterone in humans and mammals, this shows that Zn works by diminishing the enzyme aromatase Cyp19, an enzyme that changes testosterone into estradiol [28] Zinc inhibits the aromatase enzyme that converts estradiol into testosterone as a result, testosterone concentration will advance [29]. [4] reported that Zn improves the morphology and functional aspects of spermatozoa thus affecting spermatogenesis, on the other hand, this signal will be responded to by Leydig cells so that it will increase the concentration of testosterone (Figure 1).…”