What causes PMS symptoms?
One theory is that the body’s energy needs during that part of the menstrual cycle cause low blood sugar, which is known to impair self control and make people more irritable:
Numerous studies suggest that premenstrual syndrome (PMS) may be linked to impaired self-control since many of the symptoms of PMS are indicative of impaired self-control. Evidence links PMS to increased difficulty controlling emotions, attention, and fine motor movements; increased intake of alcohol, drugs, nicotine, caffeine, and food; impaired work performance, and increased stress, aggression, criminal behavior, interpersonal conflicts, and passivity. Empirical research demonstrates that self-control is metabolically expensive and, as such, can be impaired when metabolic energy (i.e., glucose) is low or processed ineffectively. The expression of PMS is tightly linked to the luteal phase of the menstrual cycle, a time in which considerable metabolic energy is allocated to the ovaries. This increased ovarian metabolic demand could, therefore, divert energy away from, and thereby impair, other processes during this phase of the menstrual cycle. Here, we propose a novel theory in which PMS symptoms are partly attributable to the diversion of metabolic energy to the ovaries and away from processes that benefit self-control.
Source: “A theory of limited metabolic energy and premenstrual syndrome symptoms: Increased metabolic demands during the luteal phase divert metabolic resources from and impair self-control.” from Review of General Psychology, Volume 14, Issue 3, September 2010, Pages 269-282