Perimenopause is the transition period leading up to menopause — when your reproductive hormone levels begin to decline.

Perimenopause typically starts in your mid-to-late 40s, but the timing varies. Some women experience symptoms in their 30s or early 40s. Perimenopause lasts, on average, about 4 years. But it can continue for up to a decade. You've officially reached menopause once you've gone a full year without a menstrual period.

During perimenopause, estrogen levels drop and you may notice more irregularity in your periods. That’s a sign you’re getting closer to menopause.

Read more about perimenopause.

Menopause is a natural part of life. Menopause isn’t just the end of your period. It’s a major hormonal shift that affects almost every part of your body — from your brain and bones to your sleep, mood, and metabolism.

You’ve officially hit menopause when you haven’t had a menstrual period for 12 straight months. This typically happens between 45 and 56.

Reaching menopause before 45 is called early menopause. Premature menopause happens at 40 or younger.

Read more about menopause.

Menopause is a specific point in time after perimenopause. Once you reach menopause, you’re in postmenopause — which lasts for the rest of your life.

Estrogen is one of the primary female sex hormones, and it serves an important function in both reproductive and overall health. Estrogen supports many important processes, from the development of secondary sex characteristics (like breast growth) to regulating your menstrual cycle. It plays an essential role in ovulation, pregnancy, and vaginal lubrication. Estrogen also has a variety of non-reproductive functions. It can impact your mood, bone health, brain function, weight, and even the condition of your skin and hair.

By the time you reach menopause, your body will have gradually stopped producing estrogen the way it used to.

The transition to menopause, known as perimenopause, can unfold over the course of several years. It’s common for estrogen levels to rise and fall unpredictably during this time. While menstrual cycles, ovulation, and pregnancy can still occur, estrogen levels will gradually decline.

Once you reach menopause — officially defined as going 12 months without a menstrual period — ovulation ends and estrogen levels drop permanently. At this time, the primary form of estrogen in your body switches from estradiol (E2) to estrone (E1).

Read more about estrogen.

Progesterone plays a key role in reproductive and hormonal health. Here’s how:

• It prepares the uterus for pregnancy. After ovulation, progesterone helps thicken the lining of the uterus, making it easier for a fertilized egg to attach and grow.

• It supports early pregnancy. Progesterone helps maintain the uterine lining, which is essential for a healthy pregnancy.

• It influences brain and mood health. Progesterone can have a calming effect by interacting with GABA receptors in your brain. This might translate to better sleep and lower anxiety, especially during the second half of your menstrual cycle.

• It balances other hormones. Progesterone helps keep estrogen levels in check. This is important for preventing symptoms like heavy periods or mood swings.

As you enter perimenopause and approach menopause, progesterone levels drop — often faster than estrogen.

This hormonal shift can cause symptoms like:

• Irregular cycles

• Heavier bleeding

• Anxiety

• Trouble sleeping

Read more about progesterone.

Estradiol is a type of estrogen, which is a group of sex hormones made by both male and female bodies.  It helps regulate your menstrual cycle. 

Estrogen levels (including estradiol) drop during menopause, which can cause symptoms like hot flashes, mood swings, and trouble sleeping.

Learn more about estradiol.

Low estrogen is a hormonal imbalance that most commonly occurs during perimenopause and menopause — a natural life stage when the body begins producing less estrogen. This shift can often bring a wave of new (and sometimes frustrating) emotional and physical symptoms.

Low estrogen is a natural part of the transition into menopause, when estrogen production declines significantly. Once women reach menopause — defined by 12 months of amenorrhea, or the absence of menstrual periods — estrogen levels remain consistently low.

Learn more about low estrogen.

Hot flashes are one of the most frequent and disruptive vasomotor symptoms associated with the menopausal transition. They involve a sudden wave of heat, usually beginning in the face, neck, or chest, that may spread throughout the body.

Episodes can last from a few seconds to several minutes, and often bring flushing, sweating, a racing heartbeat, and sometimes a sense of anxiety or unease. As the body cools, many women experience chills or shivering.

When hot flashes happen at night, they’re called night sweats. These can disrupt sleep, leading to fatigue, difficulty concentrating, and reduced quality of life. While some women only have occasional, mild episodes, others experience frequent and intense hot flashes that interfere with daily activities and emotional well-being.

Learn more about hot flashes.