What are the common causes of male breast enlargement In addition to the dominant androgens in men, there are also small amounts of estrogens produced by the testes and adrenal cortex Under normal circumstances, the male breast is in a non-developed state under the constraints of androgens. A decrease in androgen levels in the body for some reason, or a relative or absolute increase in estrogen levels, may induce hyperplasia of breast tissue. Breast enlargement in boys during puberty is a common physiological phenomenon because when boys reach this stage of development, the endocrine function in the body is gradually active and the testes produce a large amount of androgens while estrogen production also increases. Some boys have a temporary disruption in their endocrine function and secrete too much estrogen, which, combined with the increased sensitivity of breast tissue to estrogen, stimulates the growth and enlargement of breast tissue.