What leads to male breast development? is it too much estrogen or is it too much testosterone or an unbalance between the two?

Male Breast: 28M: Asks: about male breast development. ANS: Mechanisms of gynecomastia include a decrease in androgen production, an increase in estrogen, or increased availability of estrogen precursors for peripheral conversion to estrogen. Androgen receptor blockade and increased binding of androgen to sex hormone-binding globulin (SHBG) are other mechanisms. Please google for more details.