Biology Reference
In-Depth Information
This phenomenon, which requires further validation and demonstration in
other populations, has been mainly identified in girls and has caused consid-
erable concerns among scientists and even lay public. This is mainly due to the
potential adverse outcomes of early puberty, which include increased risks of
disordered behavior, cardiovascular and metabolic disease, hypertension,
obesity, and diabetes, as well as lower adult height (
Carter, Jaccard,
Silverman, & Pina, 2009; Ibanez, Diaz, Lopez-Bermejo, & Marcos, 2009;
Labayen et al., 2009; Lakshman et al., 2008, 2009; Taeymans et al., 2008
).
Of note, a very recent study has suggested that a similar trend for earlier
puberty can be occurring also in US boys (
Herman-Giddens et al., 2012
).
Such a
recent
decline in the age of puberty might be related to the influence
of different modifiers, such as the higher prevalence of childhood obesity
and/or the increased exposure to different environmental pollutants
(
Aksglaede, Juul, et al., 2009; Aksglaede, Sorensen, et al., 2009
); earlier
puberty just being a sign of disturbed homeostasis with potential serious
consequences in the long term. Yet, as mentioned above, conclusive demon-
stration of a universal trend for earlier puberty in humans is still missing
and epidemiological data must be taken with caution until such validation
is provided.
In any event, the above evidence stresses the need for a deepening of our
knowledge of the physiological mechanisms of normal puberty, and of the
regulatory networks whereby puberty and other essential body functions,
such as energy homeostasis, are jointly controlled. Indeed, in the last decade,
important developments have takenplace in this field, whichhave permitted a
significant expansion of our understanding of the basis of normal and altered
puberty (
Tena-Sempere, 2012
). In this chapter, we will provide a synoptic
overview of some of these recent developments, with special emphasis on
the identification of novel neuropeptide systems involved in the control of
the pubertal awakening of the reproductive axis, andhowthese aremodulated
by metabolic signals and novel regulatory elements, such as epigenetics and
miRNA pathways.
2. NEUROBIOLOGY OF PUBERTY: ESSENTIAL ROLES
OF GnRH AND Kiss1 NEURONS
From a reproductive perspective, puberty involves the full activation
of the activity of the so-called hypothalamic-pituitary-gonadal (HPG) or
gonadotropic axis, which is responsible for the completion of gonadal devel-
opment and the attainment of sexual phenotypic maturity (
Tena-Sempere,
