1. Environment
1.1. **Endocrine Disruptors**
1.1.1. Mechanism: interferes with HPG axis in two ways
1.1.1.1. 1) Directly affects oestrogen sensitivity through binding to oestrogen receptor OR blocking androgen receptors
1.1.1.1.1. **Phytoestrogens:** Known to be a cause of precocious puberty due to increasing oestrogen receptor stimulation at low oestrogen concentration in developing girls
1.1.1.1.2. Found in soy foods; tofu, soy sauce - common in asian diet
1.1.1.2. 2) Indirectly via affecting GnRH secretion
1.1.1.2.1. https://doi.org/10.4274/jcrpe.v3i1.01
1.2. **Stress**
1.2.1. Chronic activation of the stress system (production of stress steroids such as epinephrine, norepinephrine and hypercortisolism) have consequential negative impacts on growth, endocrine, reproductive, and metabolic function.
2. Metabolic
2.1. **Nutrition**
2.1.1. Caloric reserves
2.1.1.1. Obesity causes HPG activation causes precocious puberty
2.1.1.2. Unclear link between kisspeptin and leptin
2.2. **Energy** **metabolism**
2.2.1. Leptin
2.2.1.1. Energy signal to hypothalmus, affects puberty timing
2.2.2. Insulin + IGF-1
2.2.2.1. High insulin = increased GnRH = early puberty High IGF-1 = growth spurt
2.2.3. Ghrelin
2.2.3.1. Supresses puberty, Ghrelin = hunger, malnutrition