When abnormally large breasts develop in males, it is called gynecomastia. It is due to the excess growth of breast tissue, not excess fat tissue. The condition may occur in one or both breasts. It begins as a small lump beneath the nipple, which may be tender. One breast may be larger than the other.
Changes in Breast Size – Different Reasons and Causes
Enlarged breasts in men (gynecomastia) - Symptoms and causes - Mayo Clinic
The size the female breast is mainly due to the fat content within the breast and the milk-producing glands. Genetic factors, age, having children or not and overall body fat content are the main factors that impact on the breast size. Sometimes the breast size may fluctuate over a short period of time, like days or weeks, and this can occur for a number of reasons. Although many young girls and women do become quite concerned about these sudden changes in breast size, in most instance it is not a cause for concern. The female hormones causes enlargement of the milk-producing tissue in the breast and may also contribute to breast swelling by the way of temporary fluid accumulation.
Breast enlargement in males
The size of breasts varies among individuals and even during the course of life for a host of reasons. Unlike other appendages, the breast probably undergoes the greatest degree of changes in size and shape over years and decades. It happens in both males and females. However, it is more obvious in women who naturally have significantly larger breasts than males. For most women, the concern is when the breast size changes significantly within a short period of time — like weeks and months.
T he causes of gynecomastia have always been somewhat of a mystery. Since it is a benign condition, not much effort was put into finding what causes gynecomastia at a root level. Breast enlargement in adult men caused by excessive breast tissue growth is genuine gynecomastia [ 1 ].