Suddenly you give your daughter a bath and notice a swelling in her breasts. But how can that be? She’s still a baby—what could this be? This increase in breast size in children is called precocious thelarche1. Many parents are surprised by the evidence of breast development in infant girls. This situation can also be detected by the pediatrician during a routine check-up, so parents should be informed about what it is.

What is Precocious Thelarche?

Thelarche is the medical term for the development of breasts in girls, which usually occurs after 8 years of age and is accompanied by other signs of puberty, including a growth spurt. Precocious thelarche is considered in girls who develop small breasts (usually two centimeters or less), typically before 3 years of age. Girls with precocious thelarche do not have other signs of puberty. A girl who has begun puberty will show an increase in breast size within 4 to 6 months, but a girl with precocious thelarche can spend a year or more with little or no change in breast size, and in some cases the breasts tend to decrease in size. Usually, both breasts grow, but in some cases only one side is affected. The genitals do not show any signs of hormonal-type development or stimulation, and growth is generally not affected. Girls with precocious thelarche usually have their first menstrual period at a normal age. The occurrence is found in less than 5% of girls of white ethnicity, in 12% of girls of black ethnicity, and in 19% of girls living in Latin America with normal weight and growth values. In those who are overweight or obese, the prevalence of precocious thelarche up to eight years old is higher compared to normal-weight girls.

Causes of Premature Breast Growth

The causes of precocious thelarche are varied and may be classified as follows:

  • Breast development in newborns
  • Breast development due to exogenous (external) exposure to estrogen
  • Precocious puberty
  • Ovarian cysts or tumors

Mammary hypertrophy (breast growth) in the newborn is caused by the effect of maternal and placental estrogens in normal babies, and usually disappears in a few days or months2. Only in some cases does it persist beyond the first year of life. No interventions are needed; just observe the baby until the breast swelling disappears and returns to normal. Another common cause of precocious thelarche is exposure to external estrogens. These estrogens (female hormones) can be found in vaginal creams, dermatological products, hair tonics or other hair products, oral contraceptives, foods like soy and chicken, etc. Contact with creams containing estrogen may happen through hygiene care carried out by the mother or by another caregiver. In some girls who have precocious thelarche, small cysts are observed in their ovaries. One theory is that these cysts may produce a small amount of estrogen and then disappear, but the effect of estrogen on breast tissue may persist for a while. The other causes correspond to childhood diseases such as puberty itself. If the girl presents breast development as the first sign of precocious puberty, the situation should be monitored by an endocrinologist, who will conduct the necessary examinations.

Symptoms of Precocious Thelarche

The main and probably only symptom of precocious thelarche is the presence of increased volume in the mammary gland (generally about 1 to 2 cm), firmer than the surrounding tissue, usually painful to the touch, sometimes with asymmetric development.

Diagnosis of Precocious Thelarche

In a girl who develops breasts before the age of 3, often all that is needed is patience and observation. At this age, true precocious puberty is rare, so any girl with breast development that barely changes over time and is growing at a normal rate on the growth chart is likely showing only precocious thelarche, with no major concerns. Thus, many doctors do not order tests. Some may order blood tests, the most useful being pituitary hormone known as LH, which should be low, and the key estrogen hormone called estradiol, which should be normal for the age or slightly elevated. Some doctors will also order a X-ray of the left hand (also known as bone age), but it is rare for bone age to be significantly advanced in cases of precocious thelarche. For girls who develop breasts between the ages of 6 and 8, precocious thelarche can still occur, but precocious puberty is much more likely. If the precocious thelarche in these girls is accompanied by other symptoms of precocious puberty, such as rapid growth, the appearance of pubic hair, and other signs of puberty, it is necessary to seek a specialist to try to establish the cause of the problem and stop puberty3, since if these girls have menarche (their first menstruation) at an early age, they will generally have short stature because the growth plates will close and their growth will stop. Therefore, it is important that careful monitoring is carried out to show changes in the amount of breast tissue over time. In these cases, tests are extremely important.

Treatment of Precocious Thelarche

Once this condition is diagnosed, does not progress, and there are no complications, no treatments are needed. These girls should not be referred to a surgeon, as breast cancer is unknown at this age and surgery should never be considered. Follow-up studies have shown that it is uncommon for a girl with precocious thelarche starting before age 3 to develop true precocious puberty at a later age. These girls go through puberty at a normal age, so precocious thelarche does not leave any after-effects in those who developed the condition. See also: Accessory Breast – What is This? Photos: LuidmilaKot