I don’t know about you but, when my period comes around, I am laid out on my heating pad, queuing up my comfort show (New Girl—because I’m a millennial). Cramps are a pretty common period symptom, but your menses can affect other areas of the body, too. In fact, your cycle can cause a whole host of unexpected period symptoms—outside of cramping and bleeding.

The menstrual cycle has four phases—and they impact your entire body

As you probably know, your menstrual cycle isn’t just the days you spend cramping and bleeding. Your cycle has four distinct phases, and your hormone levels fluctuate throughout. Your cycle starts on the first day of your period when your body sheds uterine lining.

Estrogen levels are low during menstruation, but during the follicular stage, your body releases a hormone called follicle-stimulating hormone (FSH), which encourages your eggs to grow and mature. Your estrogen levels get progressively higher until ovulation when your ovaries release an egg and progesterone production increases, according to Elizabeth Poynor, PhD, MD, surgeon and oncologist at Memorial Sloan Kettering and clinical professor of obstetrics and gynecology at NYU Langone Medical Center.

Progesterone levels continue to rise during the luteal phase,  and this is when you’re most likely to experience PMS. At the end of the luteal phase, estrogen and progesterone levels drop very quickly, which initiates bleeding or menstruation. And, the cycle begins once more.

These phases serve specific reproductive purposes, but they affect more than just your uterus. Everyone’s hormonal fluctuations are different, and the symptoms that occur are unique, Dr. Poynor says. Still, she explains a few unexpected areas of the body that are frequently affected by your cycle.

1. Joint pain, soreness, and stiffness

There are estrogen receptors in muscles and cartilage, Dr. Poynor says, so changes in your hormone levels can affect your muscles and bones. Studies indicate that estrogen is connected to pain threshold, and drops in estrogen point to lower tolerance. This means that when your estrogen levels drop during your period, you can experience pain at a stronger level, Dr. Poynor adds.  If you feel surprisingly stiff and sore, warm baths and nonsteroidal anti-inflammatory drugs (NSAIDs) can help ease the pain.

2. Headaches and dehydration

If you frequently get a headache during or around your period, you’re not wrong to assume menstruation is the culprit. Drops in estrogens have been linked to headaches and even migraines. Though the reason this happens isn’t abundantly clear, Dr. Poynor says hormonal headaches can occur due to fluctuations in, you guessed it, your hormones.

Estrogen and progesterone affect neurotransmitter receptors in the brain, so fluctuations and changes can result in mood shifts or headaches. It’s not necessarily how much you have of these hormones that cause adverse symptoms; rather, it’s the rate at which they fluctuate.

Headaches might also happen during your period due to hydration levels. A 2020 study published in Frontiers in Physiology suggests that estrogen and progesterone impact how the body stores and uses water through the menstrual cycle. The researchers also suggest that dehydration can often increase pain reception, which can lead to feeling the sensation more intensely. Combined, these two factors indicate that staying on top of your water intake is a good idea.

3. Breast pain, tenderness, and swelling

If your bras suddenly feel super uncomfortable, you might be able to blame it on an ill-fitting bra, but it could also be an unexpected period symptom. Breast pain, though quite common, is usually caused by higher progesterone levels, which occur during your luteal phase, Dr. Poynor says. This is because progesterone often encourages water retention, and that can make breasts feel swollen, tender, or sore. Estrogen and progesterone also stimulate milk glands and ducts in the breasts, whether you’re pregnant or not, according to the Mayo Clinic. And this can also make your breasts more tender.

If you have unexplained breast pain that does not go away after two periods, you should check in with your medical professional, the Mayo Clinic says.

4. Back pain and stiffness

“There is a hormone-like substance called prostaglandin that causes uterine contractions, and might also affect back muscles and contribute to back pain,” says Amy Roskin, MD, a board-certified obstetrician and gynecologist.

Prostaglandins cause intermittent blood flow in the muscles, which induces contractions. During your period, you experience uterine contractions, which encourage menstrual blood flow. This is ultimately a good thing,  but those contractions can agitate nerves and muscles in your back.

If you need relief, a heating pad encourages blood vessels to expand, which improves blood flow. This can, in turn, reduce the pain from this period symptom. NSAIDs like ibuprofen help block prostaglandins and reduce pain, too, Dr. Raskin adds.

If back pain disrupts your life during menstruation, it’s important to be evaluated by a doctor, Dr. Poynor says.

5. GI discomfort, diarrhea, and gas

A 2014 study published in BMC Women’s Health surveyed 156 participants who menstruate regularly,  and 73 percent of individuals reported one or more GI symptoms, including 28 who reported having period diarrhea. So if you regularly deal with stomach issues, gas, diarrhea, or even constipation, your cycle might be to blame.

Hydration and hormone level fluctuations can contribute to GI symptoms for a few reasons. These factors affect how quickly you move waste through your body and how much gas you release.

Additionally, the colon and lower large intestine can experience friction as the uterus contracts during menstruation. This movement, because of the colon and pelvic floor’s proximity to the uterus, can loosen stool and encourage more frequent bowel movements. Every month, I forget about this and am filled with renewed annoyance about my GI-related period symptoms.

There is still a lot of research to be done about these hormones and how they impact your body. Dr. Poynor points out that studies are beginning to indicate that progesterone may have a more significant impact on the body than its more obvious menstrual cycle purposes. So, even though period symptoms are multifaceted and individualized, It’s worth remembering that you know your body best. If a period symptom concerns you—it’s always worth checking in with a provider to chat about your concerns.

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