Is acne always caused by hormone imbalances?

A hormonal imbalance is one of the leading causes of acne, and is the main reason why so many adults, not only teenagers, are affected by this skin condition. The excess of oil combines with dirt, debris, dead skin cells, and even pollutants in the air. Once this combination is complete, the pore of the skin is blocked and bacteria are allowed to infect the blockage. Although hormonal imbalances are often associated with more serious medical conditions, individuals of all ages are capable of being affected by a hormonal imbalance that can directly affect the quality of their skin.

Are underdeveloped breasts and nipples a result of hormone imbalance and will going on contraceptive pills like Ginnette get the process going or not really?

I think hormone imbalances and eating oily stuff are the two main reason for acne.