Oestrogens and 1α,25(OH)2-vitamin D3 (1,25-D3) are steroids that can provide effects by binding to their receptors localised in the cytoplasm and in the nucleus or the plasma membrane respectively inducing genomic and non-genomic effects. As confirmed notably by invalidation of the genes, coding for their receptors as tested with mice with in vivo and in vitro treatments, oestrogens and 1,25-D3 are regulators of spermatogenesis. Moreover, some functions of ejaculated spermatozoa as viability, DNA integrity, motility, capacitation, acrosome reaction and fertilizing ability are targets for these hormones. The studies conducted on their mechanisms of action, even though not completely elicited, have allowed the demonstration of putative interactions between their signalling pathways that are worth examining more closely. The present review focuses on the elements regulated by oestrogens and 1,25-D3 in the testis and spermatozoa as well as the interactions between the signalling pathways of both hormones.

The castration of stallions is traditionally performed after puberty, at around the age of 2 years old. No studies have focused on the effects of early castration on osteoarticular metabolism. Thus, we aimed to compare early castration (3 days after birth) with traditional castration (18 months of age) in horses. Testosterone and estradiol levels were monitored from birth to 33 months in both groups. We quantified the levels of biomarkers of cartilage and bone anabolism (CPII and N-MID) and catabolism (CTX-I and CTX-II), as well as of osteoarthritis (HA and COMP) and inflammation (IL-6 and PGE₂). We observed a lack of parallelism between testosterone and estradiol synthesis after birth and during puberty in both groups. The extra-gonadal synthesis of steroids was observed around the 28-month mark, regardless of the castration age. We found the expression of estrogen receptor (ESR1) in cartilage and bone, whereas androgen receptor (AR) expression appeared to be restricted to bone. Nevertheless, with respect to osteoarticular metabolism, steroid hormone deprivation resulting from early castration had no discernable impact on the levels of biomarkers related to bone and cartilage metabolism, nor on those associated with OA and inflammation. Consequently, our research demonstrated that early castration does not disrupt bone and cartilage homeostasis.

Castration of stallions is traditionally performed after puberty around the age of 2 years old. No studies have focused on the effects of early castration on osteoarticular metabolism. Thus, we sought to compare early castration (3 days after birth) with traditional castration (18 months of age) in horses. Testosterone and estradiol levels were monitored from birth to 33 months in these two groups. We quantified the levels of biomarkers of cartilage and bone anabolism (CPII and N-MID) and catabolism (CTX-I and CTX-II), of osteoarthritis (HA and COMP) and inflammation (IL-6 and PGE2). We revealed a lack of parallelism between testosterone and estradiol syntheses after birth and during puberty in both groups. An extra-gonadal synthesis of steroids was observed around the 28 month-mark, regardless of the castration age. We found the expression of estrogen receptor (ESR1) in cartilage and bone, whereas androgen receptor (AR) expression appeared to be restricted to bone. Nevertheless, with regards to osteoarticular metabolism, steroid hormone deprivation resulting from early castration showed no discernable impact on the levels of biomarkers related to bone and cartilage metabolism, nor on those associated with OA and inflammation. Consequently, our research demonstrated that early castration does not disrupt bone and cartilage homeostasis.