Polycystic ovary syndrome (PCOS) is caused when a woman’s hormones are imbalanced and often cysts form on the ovaries. PCOS can affect menstrual cycles, fertility, appearance, heart health and more. While the cause of PCOS is unknown, studies have suggested it is genetic. Symptoms may be mild at first but can become more serious as it progresses. The most common symptoms include acne, weight gain, thinning hair, irregular periods and fertility issues.