Precocious puberty is defined as an advanced age of onset relative to The onset of pubic hair may be due to abnormal or premature secretion of hormones (androgens) by the adrenal glands. Being overweight could promote this early onset.
The isolated development (= no other symptoms) of the mammary gland is sometimes observed in a 2-3 year old girl, but the nipple and areola are not modified and the vulva remains infantile. We then content ourselves with monitoring the child because the signs generally disappear in two years, but this can also (rarely) progress to genuine precocious puberty.
Likewise, the appearance of isolated pubic hair at around 7-8 years of age leads us to verify that it is not the late or partial form of a disease of the adrenal glands (congenital hyperplasia of the adrenals) but it is the most often inconsequential.
From the age of 13, if the girl still has no breast development, we speak of delayed puberty, even if pubic or axillary hair has appeared (because it depends on the adrenal glands and not the ovaries).