Hi, Thanks for posting in HCM. I understand your concern. Concerta contains methylphenidate , which is a central nervous system stimulant. It works by changing the amounts of certain natural substances in the brain. Common side effects of Concerta include: sleeplessness, nausea, dryness in mouth and decreased appetite. Other side effects include: anxiety, irritability and excessive sweating. Enlargement of breasts is not a known side effect associated with intake of Concerta. It might have caused due to hormone imbalance associated with other reasons. Kindly consult Endocrinologist for proper evaluation and appropriate management. Hope the information provided would be helpful. All the best.