Gynecomastia is a relatively common disorder. Its causes range from benign physiological processes to rare neoplasms. To diagnose the etiology of the gynecomastia, the clinician must understand the hormonal factors involved in breast development.
Male breast development occurs in an analogous fashion to female breast development. At puberty in the female, a complex hormonal interplay occurs resulting in growth and maturation of the adult female breast.
In early fetal life, epithelial cells, derived from the epidermis of the area programmed to become the areola, proliferate into ducts, which connect to the nipple at the skin’s surface. The blind ends of these ducts bud to form alveolar structures in later gestation. With the decline in fetal prolactin and placental estrogen and progesterone at birth, the infantile breast regresses until puberty .
During thelarche in females, the initial clinical appearance of the breast bud and growth and division of the ducts occur, giving rise to club-shaped terminal end buds, which then form alveolar buds. Approximately a dozen alveolar buds will cluster around a terminal duct, forming the type 1 lobule. The type 1 lobule will mature into types 2 and 3 lobules, called ductules.