Gynecomastia and Premature Thelarche: A Guide for Practitioners

  • Diamantopoulos S
  • Bao Y
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1. Stavros Diamantopoulos, MD*
2. Yong Bao, MD†

1. *Fellow

2. †Assistant Professor, Division of Pediatric Endocrinology, Department of Pediatrics, Miller School of Medicine, University of Miami, Miami, Fla

Gynecomastia is the presence of breast tissue in males. The term comes from the Greek word gyne (woman) and mastos (breast). Gynecomastia is common and often is a concern for families, but it usually is a normal part of adolescent development. Pathologic gynecomastia does occur and can be related to a serious underlying problem. Any abnormal breast development in males warrants evaluation.

Premature thelarche ( thely =female, arche =beginning) is isolated breast development in girls younger than 8 years of age. Premature thelarche usually is benign, but may signify a more complicated condition. Practitioners should know how to evaluate early breast development in girls.

A mature mammary gland consists of 15 to 25 lactiferous ducts and lobes. Development of the breast tissue anlage is identical in the male and female fetus. Before puberty, the breast consists of the same number of lactiferous ducts ending in small ductules lined with epithelial cells. It is not until puberty that mammary gland development progresses in females, reaching completion during the first pregnancy. The mature terminal alveolar buds formed in early pregnancy are called acini. The units of lactiferous ducts with their lobules compose a lobe. Lobes are separated by dense connective tissue septa.

Several hormones influence breast development. Under estrogen stimulation, ductal and stromal components proliferate. Duct growth and division result in lobules that consist of alveolar buds clustering around a terminal duct. Lobules lie within a growing stroma of loose, hormone-sensitive connective tissue that supports the mammary gland. Progesterone promotes acinar differentiation of the ductal system. Prolactin has a trophic effect on the alveolar buds, promoting acinar formation and the secretory differentiation of the mammary epithelium to support lactation. Receptors for luteinizing hormone (LH) / human chorionic gonadotropin (hCG) have been found in mammary tissue; it is believed that these hormones also may …

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  • S. Diamantopoulos

  • Y. Bao

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