Animalia

Gonadarche              1. Arche is the Greek word. Arche- beginning              2. Gonadarche refers to the earliest changes of puberty.               3. In response to pituitary gonadotropins, the ovaries in female and the testes in male begin to grow and increase the production of the sex steroids, especially estradiol and testosterone.              4. In male, testicular enlargement is the first phyical sign of gonadarche, and usually of puberty.              5. In female, ovarian growth cannot be directly seen, so thelarche and growth acceleration are usually the first evidence of gonadarche.              6. Gonadarche indicates that true central puberty has begun, while adrenarche is an independent process only loosely associated with complete puberty. ...

                         DE - SYNCHRONY THEORY OF PUBERTY   This theory is based on a finding that GnRH concentrations in the hypothalamus during prepuberty are comparable to those in the adult animals.   GnRH from the hypothalamus is controlled by an area in the hypothalamus referred to as the neural GnRH pulse generator.     Age related changes in brain morphology and neuronal cytoarchitecture may also be important. Theory Desynchrony theory proposes that the lack of GnRH stimulation of the pituitary in prepubertal animal is a result of the desynchronization of the discharge or 'firing' of the GnRH secreting neurons.  This hypothesis has some support from in vitro studies in immortalized GnRH neurons.                                       

Central nervous system (CNS) restraint hypothesis of puberty "In the 1980s, it was found that agonadal subjects had a pattern of changes in gonadotropin concentration. It was  called as intrinsic restraint hypothesis" In addition to sex steroid-mediated negative feedback, a central inhibitory system restrains GnRH release and maintains the  prepubertal  phase.   At the onset of puberty, the intrinsic CNS restraint is inhibited or is dominated by a stimulatory system.   During the last decades, considerable evidence has been gathered to support this intrinsic restraint hypothesis. Factors involved in the regulation of gonadotropin-releasing hormone (GnRH) secretion: Intrinsic restraints:     1. GABA (Gamma Amino Butyric Acid) Stimulators:     1. Glutamate     2. NPY     3. Leptin     4. TNF alpha       According to this idea, GnRH secretion is quiescent in ch...

GONADOSTAT THEORY OF PUBERTY:      The gonadostat theory was proposed by Hohlweg , 1931     1. During prepuberty, sensitivity to the negative feedback actions of gonadal steroids is highest, resulting in a low release of GnRH and gonadotropins.      2. Initiation of puberty is secondary to a decrease in sensitivity to gonadal steroid feedback inhibition , resulting in increased GnRH and gonadotropin release, until a new equilibrium level is reached in adulthood. Example:        Failure of prepubertal ewe lamb to undergo ovulation and oestrus is due to the high threshold for the positive feedback is lowered, thus there is no LH surge. At puberty, the threshold is lowered, thus allowing the pituitary to respond.