Side effects of norgestrel include menstrual irregularities, headaches, nausea, breast tenderness, mood changes, acne, increased hair growth, and others.[citation needed] Norgestrel is a progestin, or a synthetic progestogen, and hence is an agonist of the progesterone receptor, the biological target of progestogens like progesterone.[1] It has weak androgenic activity and no other important hormonal activity.[4]