Early onset of thelarche (also called premature thelarche) is a clinical condition characterized by isolated appearance of breast development, usually in girls younger than 3 years. Occasionally, a girl from three to six years of age will show an enlargement of one or both breasts. However, after age six, the beginning of breast development is actually the beginning of puberty; however, it is a very slow form of development. In addition, girls with early breast development usually do not have early periods.

Generally, breast development is a result of rising levels of estradiol (female sex hormone produced by the ovaries, adrenal gland and also the placenta during pregnancy). It is typical for a woman's breasts to be unequal in size, particularly while the breasts are developing. Statistically it is slightly more common for the left breast to be the larger. In rare cases, the breasts may be significantly different in size, or one breast may fail to develop entirely. Although breast development can occur as a part of normal male puberty, it is termed gynecomastia, and the term "thelarche" is not used with reference to male breast development.

The pathophysiological mechanisms that cause premature thelarche are unknown and have been hypothesized to result from:

  • increased breast sensitivity to estrogen
  • increased estradiol (E2) levels
  • transient estrogen secretion by follicular ovarian cysts
  • increased estrogen production from adrenal precursors
  • increased dietary estrogen
  • transient partial activation of the hypothalamic-pituitary-gonadal (HPG) axis with predominant follicle-stimulating hormone (FSH) secretion
  • increased serum SHBG (sex hormone-binding globulin) which could modify the ratio of bioavailable testosterone to estrogen, producing a relative increment in free E2

Premature thelarche does not require treatment but should be evaluated. If a doctor suspects the premature thelarche is a sign of precocious puberty (usually before 8 years of age in girls), the patient may be referred to an endocrinologist, a specialist in hormone disorders who will advise about treatment options for halting the maturation process, if required.

Symptoms

The common finding is the enlargement of one or both breasts (gynecomastia). In simple premature thelarche, there are no other signs of pubertal development, and the child is growing at a normal-not an increased-rate. There are no other signs of puberty such as the growth of pubic hair or rapid body growth.

Associated diseases

  • ovarian cancer
  • polycystic ovary syndrome (PCOS; women often have many small painless noncancerous cysts in the ovaries)
  • precocious puberty

Complications

Usually, there are no complications associated with early breast development. If there are other signs of puberty, then a physician should evaluate the child for the causes of early puberty.

Risk factors

  • obesity
  • treatment with fennel (Foeniculum vulgare)

Prevention

Premature thelarche cannot be prevented. Parents should be sensitive to their children's concerns and encourage communication so as to alleviate anxiety or fears.

Premature thelarche has been considered a variation of normal puberty due to its nonprogressive course. However, at the initial presentation, it is not always easy to distinguish it from a true precocious puberty. Precocious puberty can make a child fertile when very young, with the youngest. However, male fertility is not reduced.

Premature thelarche in the majority manifested as a self-limited condition and most patients undergo puberty appropriately. If there are no other signs of sexual maturation, this is most likely a benign (noncancerous) and follow-ups at regular intervals to those remaining symptoms above 2 years old are needed. 

The treatment is required if the condition develops in precocious puberty. In most cases, the process is normal in every aspect except the unusually early age, and simply represents a variation of normal development. In a minority of children, the early development is triggered by a disease such as a tumor or injury of the brain. Even when there is no disease, unusually early puberty can have adverse effects on social behavior and psychological development, can reduce adult height potential, and may shift some lifelong health risks.

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