What are the main causes of gynaecomastia?
Gynaecomastia commonly appears during infancy, puberty and older age. All men have the male sex hormone testosterone as well as low levels of the female hormone estrogen which controls breast tissue growth. When the testosterone to estrogen ratio changes (that is, there is an imbalance in the levels of these two hormones favouring relatively higher amounts of estrogen), breast tissue can grow. Some men with gynaecomastia have elevated estrogen levels. Sixty to 90 per cent of newborn male babies have enlarged breast tissue because of transfer of estrogen from the mother during pregnancy. As these high levels of estrogen disappear after birth, this type of gynaecomastia is temporary. Gynaecomastia is common during mid to late puberty as more estrogen than testosterone is produced by the maturing testis before testosterone production by the testes kicks in’ and reaches adult levels. Gynaecomastia appearing during puberty often goes away, and less than one in 20 affected adolescent boys ha
