Puberty Onset Influencing Factors - Anatomy & Physiology

Female Threshold Body Size

Nutritional intake of the newborn is directed towards body maintenance.
The priority of the neonate is to maintain vital physiological functions.
Non-essential processes, such as reproduction are of low priority.
As the neonate grows, energy consumption increases and the body mass increases with a relative decrease in body surface area.
This allows a shift in metabolic expenditure so that other physiological functions can develop.
The excess internal energy is converted to fat stores, and a priority is then placed on reproduction so the onset of puberty begins.
Fat accumulation alone does not determine the onset of puberty, but it is an important regulator.
All female mammals must reach a certain body size before the onset of puberty can be initiated.
Metabolic signals affect production of GnRH.

Pheromonal substances in the urine act as a stimulus to enhance the onset of puberty.
Females reaching puberty in the presence of a male (producing the pheromones) have a greater opportunity of becoming pregnant.
Pubertal onset cannot be accelerated using pheromones in animals that have not achieved the appropriate metabolic body size to trigger hypothalamic responsiveness to Oestradiol (oestrogen).

The size of the social group in which females are housed has an influence over pubertal onset.
Gilts housed in small groups will have delayed pubertal onset compared to gilts housed in larger groups.
The presence of a male in either visual or direct physical contact will hasten the onset of puberty in gilts.

Visual and olfactory environmental information is perceived by sensory neurons of the optic and olfactory systems.
Stimuli are processed by the central nervous system and converted into neural inputs to the GnRH neurons of the hypothalamus.
The hypothalamus then gains the ability to produce high frequency and high amplitude pulses of GnRH at an earlier age.