Final answer:
Hormones and body weight are two internal factors that influence the onset of puberty. Hormones such as estrogen and testosterone are responsible for the physical changes, while body weight, particularly BMI, can affect the timing of puberty.
Step-by-step explanation:
One factor that internally influences the onset of puberty is hormones. Hormones, such as estrogen and testosterone, are responsible for triggering the physical changes associated with puberty. These hormones are produced by the endocrine system, specifically the ovaries in females and the testes in males.
For example, in girls, the increase in estrogen levels leads to the development of breasts and the onset of menstruation. In boys, the increase in testosterone stimulates the growth of facial and body hair, deepening of the voice, and muscle development.
Another factor that can influence the onset of puberty is body weight. Research has shown that girls who have a higher body mass index (BMI) tend to experience puberty earlier than girls with lower BMI. This is because body fat plays a role in the production and regulation of certain hormones that control puberty.
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