All the hormones in your menstrual cycle are in a sort of dance, levels of one hormone cause another to be released, so basically your whole endocrine system is constantly talking to itself with different hormones. So what goes off the beam first isn't always clear.
That's one of the benefits of using treatments like vitex that are hormone balancers, because that puts your hole system back in harmony instead of just boosting what's missing and not knowing what the consequences will be.
Nutritional deficiencies, stress, and other health problems can affect your hormone balance, even night time light exposure can throw you off.