Puberty in girls is a moving target

It’s no secret that girls are entering puberty earlier and earlier, but a new study suggests that it happens every decade for women at the same rate as it did 3 months earlier.1

How puberty onset is measured for women can be debated, with many studies focusing on reminding a woman of her age during her first menstrual period (menarche) as the yardstick. However, new literature emphasizes breast development as the most reliable tool for measuring puberty progress in girls.

Katherine Kutney, MD, a pediatric endocrinologist at Rainbow Babies and Children’s Hospital in Cleveland, Ohio, said that, as with boys, physical indicators are a better way to diagnose the onset of puberty in the clinical setting.

For both boys and girls, the puberty process is triggered by the activation of the hypothalamic-pituitary-gonadal (HPG) axis. In boys, this causes testicular growth, which is the first clinical sign that a man has entered central puberty. For girls, although the first menstrual period can traditionally be considered a sign that puberty has started, it actually starts with thelarche or breast development.

Tanner staging, also known as the sexual maturity scale (SMR), is the standard system for measuring progress through puberty, Kutney said. For boys, this scale assigns stages to indicate progress through puberty based on pubic hair and genital development. For girls, the scale uses measurements of breast tissue and public hair development.

The development of pubic hair, a process called adrenarche, can occur at the same time as thelarche, but is not always the case. This process, which is activated by the release of female sex hormones, stimulates pubic and armpit hair growth, the development of adult body odors and acne.

Tanner staging for women2

Pubic hair

Stage 1: no hair Stage 2: light, fluffy hair Stage 3: thicker, darker (terminal) hair begins to develop Stage 4: terminal hair covers the entire pubic triangle Stage 5: terminal hair covers the entire pubic triangle and extends beyond the groin fold to the thigh

Breast Development Scale

Stage 1: No palpable glandular breast tissue Stage 2: A breast bud can be felt under the areola Stage 3: Breast tissue can be felt outside the areola, but there is no further development of the areola itself Stage 4: The areola develops above the contour of the areola breast Stage 5: The areola retracts into the contours of the rest of the breast and acquires darker pigmentation, papillae development and nipple protrusion

Earlier puberty onset in girls has been noted for some time, but the 2020 research suggests it’s advanced to the point where guidelines may need to be amended to redefine precocious or “early” puberty designations. Kutney said the average onset of puberty for girls is around age 10, but it can occur as early as age 8 for girls of African American and Hispanic ethnicities. The upper age limit for onset of puberty in girls is 12 years, she added.


1. Eckert-Lind C, Busch AS, Petersen JH, et al. Global secular trends in age at puberty onset assessed by breast development in girls: a systematic review and meta-analysis. JAMA Pediatrician. 2020;174(4):e195881. doi:10.1001/jamapediatrics.2019.5881

2. Emmanuel M, Bokor BR. Tanner internships. Stat Pearls Publishing. 2021

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