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Do you have period problems or thyroid issues? Maybe your have PMS or fibroids? You may have gotten your Vitamin D tested as part of the lab tests I recommend people get as part of their full hormone panel and for good reason; it affects both our pituitary development and can have an affect on several hormonal conditions.

What is Vitamin D?

It is a hormone like vitamin which controls calcium levels in our bodies. It can also help us to absorb nutrients such as iron, magnesium and zinc. It is essential for a number of healthy process as covered in this blog post, but it is also essential for happy and healthy hormones. It can be obtained from sunlight if we are getting adequate exposure and from foods such as oily fish. You can find out more about it in this blog post.

In truth, we are only starting to understand the impact of vitamin D on our health and there are so many studies being done on vitamin D, so I'm looking forward to seeing what else it impacts. But for today, let's look at how it affects your periods.

Pituitary Development

Our hormonal cycle begins with our pituitary gland. Out pituitary is given signalling from our pineal gland telling it what hormones are in the body and whether to increase or decrease those levels. It produces hormones such as Follicle Stimulating Hormone (FSH) and Lutenising Hormone (LH) which both kick start the menstrual cycle and trigger ovulation. It also releases Thyroid Stimulating Hormone (TSH) which is essential to get your thyroid working at the right levels. It also affects other hormonal levels that have an effect on periods but for simplicity, we'll stick to those main ones for today.

For this reason, we want our pituitary gland to develop in a healthy way and free of tumours which can cause it to produce too many of some hormones or not enough of others. Which is why this studying showing that pituitary tumours can form when there is a deficiency of vitamin D is important.

As such it is important that we ensure adequate vitamin D levels throughout childhood and puberty as well as adulthood for optimal reproductive functioning and healthy periods.

In my adult women clients, I ask them to get tested and looks for levels between 50-70 ng/mL. It is important that you test and retest your levels when supplementing with vitamin D.

Blood Sugar Regulation

Blood sugar has a huge impact on our hormones. When it isn't regulated it can cause inflammation and raised cortisol levels which affect periods big time. It can also cause increased levels of insulin which can lead to Poly Cystic Ovarian Syndrome (PCOS), insulin resistance and Type 2 Diabetes. This is because the more insulin we have, our body reduces the sensitivity, so we need more to do the same job. Eventually, our pancreas secretes more and more and for the same blood sugar levels until it can no longer meet demand and it gives up.

When any of these happen, we can find that it takes us longer to ovulate, increasing cycle length and our luteal phase, the phase between ovulation and menstruation, shorter. Eventually, this can lead to anovulatory cycles, and increased insulin can stimulate the ovaries to produce testosterone.

Women with stress, inflammation and PCOS tend to have less regular periods, heavier periods when they do come, that can last for a long time and be super painful.

Hashimotos Thyroiditis

Hashimotos is an autoimmune disease and the biggest cause of hypothyroidism (where you are not making enough thyroid hormone). One of the biggest issues with thyroid is how it affects your reproductive system; symptoms include heavy periods, painful periods, shortened luteal phase, infertility, sub fertility, and miscarriage.

Whilst the overall treatment for Hashimotos should be an elimination diet to test for common food sensitivities, especially gluten, dairy, soy and refined sugars, adequate vitamin D has been shown to slow down the development of this disease.


Once cause of heavy periods are benign growths of uterine tissue called fibroids. Whilst your womb can gain an extra 2 lbs in weight with endometrium (womb lining), in women with fibroids this can be an extra 9-11 lbs. This means not only is that more pressure on the pelvic cavity pressing on your internal organs (ouchie), periods will be heavier and more painful too.

Whilst fibroids usually require oestrogen detoxification to reduce and improve them, this study shows that vitamin D slows down fibroid tumour progression and in this study it even reduces fibroid size.


If you suffer PMS, then you could be in for some good news, vitamin D can help. PMS is a catch all term for any symptoms in the pre-menstrual time period, however, this study shows that getting adequate amounts of vitamin D can help the mood disorders that many women experience during this time.

This kind of makes sense intuitively, as most of us feel better in sunshine and find out mood lifts, and sunshine increases vitamin D.

Wow, I bet you didn't realise vitamin D could affect your periods in so many ways. If you want to know more about vitamin D and how to increase your levels, check out this post.

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Find our more about Sunscreen and Your Hormones

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