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Gillian Goddard

3 minute read Gillian Goddard

Gillian Goddard

Is It PMS or Perimenopause?

Q&A on how to tell the difference between your symptoms

Gillian Goddard

3 minute read

How do I know if my symptoms are PMS or perimenopause? I am 40 years old and over the past six months have developed really bad hot flashes, acne, mood changes, and irregular cycle lengths. My doctor said that because they are often associated with my cycle (i.e. more symptoms leading up my period) that it is probably PMS. Is this true, and does it impact the type of treatment I receive?

—Ashley

In the late-reproductive stage, the symptoms associated with your period can overlap with perimenopausal symptoms such as hot flushes, night sweats, headaches, and irritability. This is because what is driving the symptoms around your period are the same hormonal fluctuations that trigger symptoms in perimenopause: low estrogen levels. 

In brief, as our ovaries age, it takes more follicle-stimulating hormone (FSH) to prepare an egg for ovulation. That FSH also stimulates estrogen production. So estrogen levels rise higher and then fall lower than they did in our 20s and 30s. 

an adult sitting and holding the glasses and one hand on head
Matilda Wormwood / Pexels

More than 40% of women enter the late-reproductive stage in their early 40s. So it is not unusual that at age 40 you would be having these types of symptoms leading up to your period when estrogen levels are always dropping. 

One distinguishing characteristic of the late-reproductive stage is that periods are still regular. Perimenopause begins when menstrual periods become irregular — that is, the cycle length from the first day of one period to the first day of the next varies by more than seven days. So if you are having a 21-day cycle followed by a 36-day cycle followed by a 24-day cycle, that would be consistent with perimenopause. 

Age 40 is young to be experiencing perimenopausal changes like irregular menses. And there are other hormonal changes, like hypothyroidism and high prolactin, that can cause irregular menstrual periods. As a result, if you are under age 45 and your periods have become irregular, many of my endocrinology colleagues and I would recommend blood work to look for other causes for your irregular periods. 

As for treatment, assuming your symptoms are signs that you are in the late-reproductive stage or perimenopause, some of the same treatment options are indicated for both. For women in their 40s, combination birth control pills, containing both estrogen and progestin, are a great option. They provide a stable dose of estrogen throughout the month and can even be taken continuously if symptoms recur when you take the sugar pills at the end of the pack.  

Ultimately, the difference between PMS symptoms and perimenopausal symptoms in your 40s is whether or not your periods are regular. Birth control pills can be a great treatment option in both cases, but women under age 45 should be evaluated for other causes of irregular periods. 

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