Are there official recommendations for treating gynecomastia?

Depends on the cause. Gynecomastia can be caused by many things, including medication side effects, hormonal imbalance, street drugs and alcohol, liver failure and cirrhosis, kidney failure, hyperthyroidism, tumors (pituitary, adrenal, testes), hypogonadism (low testosterone), malnutrition...The recommendations depend on the cause.
Surgery Helpful. Assuming a young man has achieved a long-term stable weight and there are no “causative agents” involved, surgery may be indicated to treat persistent gynecomastia. It is often best treated with partial excision of the prominent glandular tissue as well as liposuction surgery of the peripheral chest area. Skin excision may be necessary in some cases.
Some consensus. Like big or unusually shaped noses gynecomastia can seriously interfere with self confidence in many individuals and hence can be emotionally but not physically disabling. If there is any unusual rapid growth, pain, discharge or color changes a visit to your physician is indicated. Mammography and breast biopsy can help diagnose problems that require surgical attention.
Gynecomastia. Depends on your age. If young teens, wait until mature to twenties. If persists surgery is indicated. Smoking marajuana makes it worse.