The increase in activity of the adrenal glands just before puberty WordNet 3.0 & Open English WordNet

Adrenarche is an early stage in sexual maturation that happens in some higher primates and in humans, typically peaks at around 20 years of age, and is involved in the development of pubic hair, body odor, skin oiliness, axillary hair, sexual attraction/sexual desire/increased libido and mild acne. Wikipedia

Stage of higher primate sexual development Wikidata

A stage of maturation of the cortex of the human adrenal glands, related to puberty, typically occurring between the ages of six and ten years and involving both structural and functional changes. Wiktionary

Stage of maturation. Wiktionary (translation)