Background: The control of male fertility requires accurate endocrine, paracrine
and autocrine communications along the hypothalamus-pituitary-gonad (HPG) axis. In this
respect, the possible interplay between upcoming/classical modulators of reproductive functions
deserves attention in that may be a successful tool for the future exploitation of new
potential therapeutic targets in the treatment of fertility disorders.
Methods: In this review we will discuss upcoming data concerning the role of kisspeptins,
the products of the Kiss1 gene, and estrogens - classically considered as female hormones -
as well as their possible interplay in testis.
Results: Kisspeptins, via the activation of kisspeptin receptor Gpr54 represent the main gatekeeper
of the hypothalamic Gonadotropin Releasing Hormone (GnRH) centrally modulating
the onset and maintaining reproductive functions. As a consequence, the loss of kisspeptin
signalling causes hypogonadotrophic hypogonadism in humans and animal models. In spite
of the well recognized functions at hypothalamic levels, recent data strongly support direct
production and activity of kisspeptin in testis and its involvement in the control of Leydig
cells, germ cells progression and sperm functions. Similarly, estrogens exhibit high impact
on proliferative/apoptotic/differentiative events in testis, thus resulting as local key modulators
for the production - but also for the release, transport and maturation - of high quality
Conclusion: This review summarizes the upcoming data from experimental models and humans
concerning the testicular activity of kisspeptins and estrogens to preserve male fertility.
Mutual enhancement of kisspeptin and estradiol signalling for the progression of
spermatogenesis has also been discussed.