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Originally published on 29th August 2017 Last updated on 14th January 2020
Along with many of the other symptoms of hypothyroidism, menstrual issues is a common one. Thyroid hormone is needed for pretty much every function and cell in the body so when you’re hypothyroid, many processes — including your menstrual cycle — can be affected.
The direct link between thyroid disease and menstrual cycles is not well understood by many medical professionals just yet, but there are certain patterns we know to be true, going by many patients’ experiences and symptoms. Hypothyroidism can lead to irregular menstrual cycles, non-ovulation and struggles to conceive. , , 
One of these is heavy periods, also called ‘menorrhagia’, a term I was given and diagnosed with at sixteen-years-old when I visited the doctors complaining of my period only getting heavier each month, since I started them at twelve-years-old.
Heavy periods or Menorrhagia is defined as excessively heavy or prolonged menstrual bleeding, such as soaking through a sanitary pad every hour for several hours or more, passing large blood clots (hypothyroidism and large blood clots during periods are common) or your period lasting longer than five days, which is seen as the average duration of a period. And even if you think a ten day long period is normal, like I did for years, I promise you it’s not.
My periods were lasting for ten days, if not longer, and I was leaking through the heaviest pads I could find, every half an hour. I’d miss days off school or have to come home to change, every time I was menstrutaing.
I dreaded my period and regularly avoided leaving the house where I could. For me now looking back, it was a bit of a warning sign of my impending hypothyroidism. I suspect I’ve always had hormonal issues and imbalances, namely oestrogren dominance, which likely contributed to me triggering Hashimoto’s and thus, my hypothyroidism.
With the heavy and long periods, I also experienced dysmenorrhea, particularly painful periods. Some discomfort is expected when your body is shedding itself from the inside, sure, but pain that leads to you taking time off work or school isn’t normal.
This commonly includes backache, headache (migraines) and those famous stomach cramps (period pains). If yours are excessive or have you curled over in pain, they may well be caused by your thyroid problem.
Irregular or sporadic periods, e.g. going a month between having one and then two months before another and three weeks before another, can also be a symptom of hypothyroidism and so can ‘Amenorrhea’, when periods stop altogether.
Amenorrhea can also be a sign of hyperthyroidism, so it’s definitely worth having a full thyroid panel ran to get a good insight into what’s going on. If you have irregular or sporadic periods, like me, this can be really frustrating and even anxiety inducing. If your doctor won’t run a full thyroid panel, you can find out how to do it yourself here.
As well as a full thyroid panel, I would suggest looking into your salivary cortisol levels and checking for adrenal dysfunction (note: it is more accurately referred to as hypothalamic-pituitary axis dysfunction).
High cortisol levels can rob your body of progesterone, causing an imbalance known as oestrogen dominance, and this can cause a myriad of problems, such as irregular periods or periods that disappear for two or three months, or simply become so irregular that you’re not sure when to expect them. This happened to me. And adrenal dysfunction is extremely common among thyroid patients.
Hypothyroidism and adrenals issues can also cause periods to come knocking more often than normal, a condition known as ‘Polymenorrhea‘.
With this, you may find that your period comes more frequently than it should, every twenty-one days for example, instead of the average twenty-eight day cycle.
A sex hormone imbalance such as low progesterone and too much oestrogen, common with hypothyroidism and adrenal dysfunction, is believed to be at fault, as your low progesterone level means the luteal phase can’t be sustained for long enough, so it’s cut short, bringing on your period sooner and harming chances of falling pregnant. More on that below.
Something else to mention, any teenage girls who are yet to start their period and are approaching their late teens, should be tested for a potential thyroid problem, as it could be the reason for delayed menstruation.
In terms of fertility, hypothyroidism can also be involved there.
Thyroid hormones directly affect the uterine lining, causing infertility or miscarriages to occur when they are abnormal. As well as complications during pregnancy, some women with low thyroid levels may even struggle to fall pregnant at all.
Hormones TSH (thyroid stimulating hormone) and TRH (thyrotropin-releasing hormone) are ramped up when thyroid hormones such as Free T3 and Free T4 fall too low; TRH to stimulate the pituitary gland to release TSH, which then instructs the thyroid gland to release more thyroid hormones T3 and T4.
Infertility can therefore occur when TRH, which is also responsible for stimulating the pituitary gland to release prolactin, causes the increased prolactin to interfere with the ovulation process, when thyroid hormones are low.
The increased prolactin levels (prolactin is also important for promoting lactation) can prevent the ovaries from releasing an egg each month, which makes it more difficult to conceive. Therefore, ensuring your thyroid levels, TSH, Free T3 and Free T4, are all optimal is crucial when trying to conceive.
Hypothyroidism may also cause a short luteal phase which can affect fertility. The luteal phase is the time between ovulation (the release of an egg) and the start of your period. In order to become successfully pregnant, your body needs to be in its luteal phase for around fourteen days, to allow a fertilised egg enough time to successfully implant and start to develop. If your luteal phase is too short, a successfully fertilised egg may not have the chance to implant and so becomes removed from the body during your period. Thus affecting the ability to fall pregnant.
See Also: Preparing for Pregnancy Blood Test
So, What Can You Do?
I hear from a lot of thyroid patients who complain that changes to their periods or menstrual cycle only started after commencing thyroid medication – and so they believe that their thyroid medication is the culprit for these changes. However, thyroid medication itself won’t cause changes to your period, but instead it often brings to the surface other hormonal issues you may have going on, such as a sex hormone imbalance or adrenal fatigue. Both of which can cause period changes along with less than optimal thyroid hormone levels.
So, with any menstrual issues or abnormalities, a full thyroid panel testing Free T3, Free T4, TSH and thyroid antibodies should be run, with Reverse T3 if possible, but also a 24 hour saliva test for cortisol (adrenals) and blood test for sex hormones.
You should ideally test your progesterone at its peak, around day 21 of your cycle (this may differ or be difficult to predict if you have an irregular cycle), and oestrogen Days 3-5. Testosterone can be tested at anytime during the month and checking FSH (the ovarian egg supply) can also be beneficial.
Do ensure your thyroid levels are optimal as an initial step. Many of the problems mentioned in this post can be solved with optimal thyroid levels.
Also ensure other possibilities such as PCOS and endometriosis are checked, too. These can go hand in hand with thyroid disease.
You can click on the hyperlinks in the above post to learn more and see references to information given but more information can also be found at:
Rachel Hill is the highly ranked and multi-award winning thyroid patient advocate, writer, speaker and author behind The Invisible Hypothyroidism. Her thyroid advocacy work includes writing articles, authoring books, producing her Thyroid Family email newsletters and speaking on podcasts, as well as being a founding board member for the American College of Thyroidology. She is well-recognised as a crucial contributor to the thyroid community and has a large social media presence. Her books include “Be Your Own Thyroid Advocate” and “You, Me and Hypothyroidism”.