Amenorrhea is the abnormal absence of a period. There's not a blanket reason this occurs, though the simplistic reason is "hormonal imbalance." But this happens for many reasons: poor nutrition or absorption which fails to provide the building blocks needed to create hormones, extremely low body fat (like you would see in extremely fit, lean athletic women and/or anorexics), tumor growth, and a myriad of other reasons. You need a good diagnosis and differentiation for this. Treat intelligently based on your diagnosis using as few points as possible so as not to confuse the body about your intention in treatment.
That said, look at the Master Tung points below. These points can be used for a number of gynecological problems including amenorrhea, dysmenorrhea, and ovarian cysts. Why are all treated with the same points? Because Master Tung’s acupuncture is based on channel systems and classical acupuncture. This is a targeting system, so the Qi flows to the entire affected area because that’s where the Qi of the channel flows. All of these problems are a result of dysfunction of the same channels with different expressions.
Left side:
Right side: