Gynaecomastia is the development of mammary glands in the males and the main reason is the hormone inbalance. While all men have some level of oestrogen but usually have much higher level of testosterone.
Newborn baby boys : Newborn baby boys may be affected by gynaecomastia because oestrogen passes through placenta from mother to baby. This condition is temporary and will disappear within weeks.
Puberty : During puberty, hormone levels vary. If the leves of testosterone drops, oestrogen can cause breast tissue to grow. This is resolved as boys grow older when hormone levels become more stable.
Older stage : As men grow older, they produce less testosterone while oestrogen secretion is enlancedand this inbalance results in gynaecomastia.