Male breast over-development or Gynecomastia (colloquially known as man boobs) is generally a bilateral and symmetrical anatomical abnormality of male breast maturation. Occasionally due to endocrine hormone abnormalities, the process most often occurs with no apparent cause in adolescent or fully mature males. Obesity may be a contributing factor, but equally often the problem is simply due to undesirable pectoral fat storage and some element of glandular tissue enlargement in the male breast. Certain medications may also contribute to the development of Gynecomastia, especially drugs used for hormonal treatments of some male cancers.
Gynecomastia usually does not signal the presence of any "disease", but since Breast Cancer does occasionally occur in older males, the finding of unilateral (one-sided) male breast enlargement must be considered a particular danger, and biopsy is usually warranted.
Although the anatomical finding of Gynecomastia does not usually represent a disease, it is a source of teasing, and anguish, in adolescent males, and certainly a source of significant embarrassment in adult men as "man boobs" are regarded as feminine or a sign of low fitness.