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Premature Breast Development in Preschoolers

Any parent would worry if they saw signs of puberty in their toddler. But in reality, premature breast development in little girls is fairly common, with a peak incidence anywhere from 6 months to 2 years of life and the other around the ages of 6-8 years. Studies have shown that premature breast development affects about eight percent of white girls and more than 20 percent of black girls under 8 years old.

Premature thelarche is the medical term for early breast development in girls under 8 years old without any other signs of sexual maturation. Little girls with this condition will have the onset of gradual breast development over a several month period. They will often complain that their breasts are tender to the touch. This can occur in both breasts or just one breast and may resolve spontaneously after a period of time.

So what causes early breast development in little girls? There are a few possibilities:

The breast tissue becomes extra sensitive to the normal estrogen that is in a little girl’s body.

There is an imbalance in the ratio of estrogen to androgen, another hormone that produces sexual characteristics.

The hypothalamic-pituitary-ovarian axis is too active. In other words, usually the puberty hormones in the brain are “turned off” until the onset of puberty. In premature thelarche, it is thought these hormones are partially active.

Obesity is another well-recognized cause of premature thelarche. Due to a complicated relationship with the adrenal glands and fat cells, there is an increase in estrogen production. Sometimes obesity alone can explain premature breast development in a young child.

Occasionally, little girls who are exposed to too much estrogen outside their body can develop premature thelarche. Examples include:

Ingestion of estrogen-primed foods

Accidental ingestion of oral contraceptives

Exposure to estrogen-containing creams

Exposure to herbal medications, some of which mimic estrogen

Exposure to certain hair care products that contain estrogen

Once these outside estrogen sources are eliminated, most little girls will have a regression of their breast development.

Infant soy formula has also been suggested to contribute to premature thelarche but there is insufficient evidence to recommend avoiding foods containing soy all together.

Laboratory testing is usually not helpful in the investigation of premature breast development. The pediatrician may order a simple X-ray called a “bone age” to determine if your child’s bones are maturing too fast, a sign of true early puberty.

There is usually nothing to worry about if your little girl has premature thelarche. By definition, this condition is benign and does not progress over time. However, a small percentage of girls will go on to develop other signs of early puberty, so close follow-up is recommended. If your girl also develops other secondary sexual characteristics, such as underarm hair, pubic hair, rapidly increasing height, body odor, or acne, she should be evaluated by a pediatrician right away as these are signs of true precocious puberty.


  • Pediatrics in Review
  • Gynecomastia and Premature Thelarche.
  • Precocious Puberty.
    Saunders Manual of Pediatric Practice.

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