What Causes A Light Period?
Gaining Or Losing A Lot Of Weight

Your weight and body fat can affect your period and cause irregularities. Your period can become irregular if you are very underweight because your hormones are not functioning as they normally would. A low body weight can disrupt hormone production and this, in turn, may cause lighter menstrual periods. In addition, extreme fluctuations in weight can cause inconsistencies with your menstrual cycle. It's important to eat a healthy, balanced diet and avoid gaining or losing a lot of weight in a short time period. Eating disorders, such as anorexia nervosa and bulimia often lead to low body weight. This will upset the balance of hormones that control your menstrual cycle and cause irregular or light periods.
Hormone Imbalance

Hormones are a big part of a woman's menstrual cycle, and an imbalance will more than likely affect your period. The two hormones responsible for your cycle are estrogen and progesterone. Their amounts increase and decrease at various points throughout your cycle, and any fluctuation will affect your period. For example, estrogen is responsible for thickening the lining of the uterus, so an insufficient of the hormone will result in a thinner lining. There will be much less shedding and bleeding in that case. High levels of testosterone can also cause light periods. High levels of this hormone may alter the menstrual cycle by suppressing ovulation. If your periods have suddenly become much lighter, it may be a sign of a hormone imbalance. Your doctor can run a hormone test and prescribe the proper medication to get you back on track.