Puberty in humans is the result of changes in the hypothalamus, which result in an increased secretion of GnRH, which then stimulates an increased secretion of luteinizing hormone LH.
The hypothalamus is the part of the brain that connects your nervous and endocrine systems. GnRH refers to the gonadotropin-releasing hormone, which controls the luteinizing hormone and is activated during puberty. Luteinizing hormone is the one responsible for triggering ovulation and estrogen in women, and testosterone in men.