The exact mechanisms involved in the onset of migraines are highly complex and have been the subject of extensive research for several years. They are thought to be linked to abnormal neuronal excitability and influenced by numerous factors, including genetic, hormonal and environmental factors.
As there are different types of migraine, there are also different causes, such as:
A Drop in Oestrogen
With regard to hormonal migraine, the sudden drop in oestrogen levels during the premenstrual period is thought to be a triggering factor. During the menstrual cycle, our oestrogen levels fall moderately for the first time at the time of ovulation, and then more sharply for a second time at the end of the cycle, just before the onset of menstruation. It is this hormonal drop that is thought to contribute to the onset of migraines.
Fluctuations in oestrogen levels, whether natural or synthetic (as is the case with the contraceptive pill), have several effects within the body:
An increase in the production of histamine, a molecule involved in the allergic response which, when present in large quantities, contributes to headaches
An increase in the production of prostaglandins, molecules involved in acute and chronic inflammation
A disruption in the balance of neurotransmitters such as serotonin – commonly known as the ‘happiness hormone’ – and glutamate, an excitatory neurotransmitter in the nervous system
Sensitisation of the cells surrounding the trigeminal nerve, which are connected to the blood vessels in the head
Next, we'll look into inflammation, a well-known factor.
Inflammation
Let’s take a look at a well-known mechanism: inflammation. It is a natural reaction of the immune system triggered by an attack: an injury, a viral, or bacterial infection, a burn, a lesion, etc. This mechanism is very often accompanied by pain, redness, swelling and a sensation of heat.
During menstruation, the body releases large quantities of prostaglandins to promote uterine contractions and expel menstrual blood. Levels of these inflammatory substances are higher in women suffering from dysmenorrhoea (period pain) and, more generally, in women with an imbalance between oestrogen and progesterone. This inflammatory state in the body contributes to the onset of catamenial migraines.
For further reading, see also the article: Natural Anti-Inflammatories.
What is known as ‘oestrogen dominance’ or ‘relative hyperoestrogenism’ can therefore contribute to migraines. Indeed, progesterone tends to have anti-inflammatory effects and counterbalances the harmful effects of oestrogen. Women who do not produce enough progesterone in the post-ovulatory phase relative to their oestrogen levels are predisposed to premenstrual syndrome, dysmenorrhoea, and hormonal migraines.
Stress
It can, of course, exacerbate catamenial migraines by negatively affecting progesterone production, promoting inflammation, and disrupting the balance of the nervous system.
Dehydration
Dehydration can also trigger headaches and migraines, particularly during periods of intense physical activity when the body loses a significant amount of fluid. If the body does not receive sufficient water and electrolytes, brain function is disrupted and the mechanisms underlying migraines may be exacerbated.