I don’t want kids (and certainly did not at 17), so not having a period felt to me like a secret blessing. No more of the hassle of a period!
However, I learned through reading books like No Period. Now What? that having a period is a very important marker of body health. Not just for bones and the heart, which are often talked about, but also the brain.
When someone doesn't a have a period, that also means they have low estrogen.
Chapter 7 of No Period. Now What? covers the negative effects of not having enough estrogen, which I include excerpts of below. The emphasis on these excerpts is mine.
The bottom line is: “Estrogen appears to be highly protective of your brain cells; if they are not getting that protection in pre-menopausal years, there may be an earlier onset of neurodegeneration. Recovery from HA restores the protective effect.”
Note: HA means hypothalamic amenorrhea and HRT means hormone replacement therapy
““As we discussed regarding the heart, estrogen promotes vasodilation, i.e., elasticity in your arteries (remember the normal balloon versus the difficult-to-blow-up balloon animals?), which makes it easier for the heart to pump blood. This elasticity also leads to a better blood supply to the brain. There is evidence that estrogen enhances the building of new nerve connections and prevents nerve cell death. In addition, new evidence suggests that many neurodegenerative diseases are due to long-term, low-level inflammation in the brain, caused by a type of cell called “microglia cells.” Microglia are turned off by estrogen and progesterone, reducing inflammation.”
“The evidence suggesting a link between low estrogen and neurodegenerative disease comes from two sources, one being the long-term follow-up of patients after surgical menopause. There is a clearly demonstrated 1.5- to 2-fold increased risk of dementia in these women with chronically low estrogen, as well as an increased risk of death from neurological disease. The risk was highest in women who had the surgery younger than 45 years old and did not use HRT, which may be a good model for what may occur with long-term HA. Studies in animal models have shown similar effects.”
“High bone density, which equates to high estrogen exposure, was associated with better performance on memory tests.”
“There are studies that suggest that low lifetime estrogen exposure is linked to a higher risk of dementia, Parkinson’s disease, and Alzheimer’s disease. Much of this is based on extrapolation from effects of low estrogen seen after menopause, which is not an unreasonable comparison. With HA, our hormones are low and not increasing throughout the month as they should be, similar to the hormonal profile post-menopause.”
“Although there haven’t been studies on whether the standard hormonal treatments are helpful, estrogen and progesterone supplementation in women following surgical menopause does show decreases in the risks of some neurodegenerative disease.”
Here's some more science on how not having a period negatively impacts the brain. From this article: https://www.verywellmind.com/brain-starvation-and-recovery-in-anorexia-nervosa-1138303
“Participants who currently had lost their menstrual cycles or had irregular menses showed significant deficits across a broad range of many cognitive domains including verbal ability, cognitive efficiency, reading, math, and delayed verbal recall (even if the structural brain changes had resolved).”
“Menstrual function may be a mediator and a better predictor of cognitive recovery than weight (for females) and that full cognitive functioning may not return until menstruation has been maintained for at least six months. This is one reason why the return of and continued menses is such an important marker of recovery.”
“They report brain healing is that they notice an improved state, “like the patient is coming out of a fog.””
“Individuals with AN are typically cognitively impaired and require sustained time at a healthy weight for cognitive impairments to fully improve. Yet, it is partly the cognitive symptoms of AN that make sufferers believe there is “nothing wrong” with them and thus reject treatment, which is a condition called “anosognosia.””
The bottom line: what to do
Naturally having higher levels of estrogen and other hormones is better than going on hormone replacement therapy. How do you naturally increase your estrogen levels, as an underweight person? Eat more. Restore your period. That will indicate that your brain is finally better-protected.