Ovulatory problems can be caused by many different factors. The condition we call polycystic ovarian syndrome is a spectrum of abnormalities that occur due to many different reasons. Some women gain wieght, and the increase fatty tissue associated with obesity produces hormones (estrogen) that induces this spectrum of symptoms. Some women have alterations in how the stimulatory hormones are produced at the level of brain (hypothalamus), which induces this ovulatory disorder. For others, insulin interferes with egg growth at the level of the ovary, inducing this ovulatory disturbance. It is different for every woman, and not everyone has each and every symptom associated with PCOS. There is no ONE CAUSE of the spectrum of symptoms we call PCOS.
For some, Vitamin D may have a role, but it is not the cause of PCOS for everyone. Most individuals are Vitamin D deficient, thus replacement should be considered for all. It is easy and harmless, and if it helps, that is great. But we know that the reason women don't get pregnant with PCOS is because eggs are not being released, and regardless of the true individual cause of PCOS, we can effectively stimulate egg growth for many women with PCOS. Some women may need the use of injectable gonadotropin medications, or even IVF (which uses these medications), but the ovulatory disturbance is almost always able to be corrected.
It is not easy to find something that will restore normal ovulatory cycles in some women with PCOS. For many, it is hard to lose weight, or simple medications such as metformin alone don't work. The same is true for Vitamin D. It may be related to the cause of a hormonal distrurbance for some, and for some it may be helpful. But many women still have PCOS with adequate Vitamin D levels, even while supplemented with Vitamin D also.
PCOS or failing egg reserve?
I am in a similar situation. I am 34 and lean, I was tested and my AMH was 2.7, then retested 2 months later and it was 9.9! I just had an antral follicle count and they found 11 one the right and 20 on the left. The other indicators of PCOS are excess facial hair and acne. My sister has PCOS with insulin resistance- she is quite overweight. She also has (natural, fraternal) twins.
My cycle is on the shorter side- generally about 24 days, with a 12 days luteal phase. I am definitely ovulating, and have had 4 miscarriages this year. The furthest I got was 5 and a half weeks, the others failed to progress beyond around 4 weeks.
It's been a very confusing time- one minute I'm being told that my ovarian reserve is very very low, the next minute that it is only on the low side, and now it doesnt look like my AMH has much to do with anything because I have so many follicles i could have PCOS.
I am desperately trying to find what is causing these miscarriages, so that we can move forward and have a second child. (We are blessed to already have a 3 year old son, who was conceived naturally and easily).
What is going on?
Recurrent pregnancy loss can be difficult to address. Most miscarriages are due to embryo abnormalities that often originate in the egg, and these types of miscarriages occur more commonly as ovarian function becomes poor and as women age.
But you have no other indication for the diagnosis of decreased ovarian reserve. You may still have abnormalities with egg production that does not allow a "good" egg to be produced, but what that problem is, we have no means to test for. At times, especially when we do IVF and we can see what eggs look like and we can see how embryos grow and what quality they are, we determine that a woman is likely producing poorer quality eggs than we expect for age. Often, women are told they have "decrease ovarian reserve" or oocyte quality issues. Why we see that at times is unknown, but the changes seen are likely contributing to those individuals infertility and possibly miscarriage.
However, if you have the clinical findings of PCOS, some studies have suggested that higher insulin levels may affect early pregnancy more often, and miscarriages can occur more commonly. Some studies have also suggested that medications like metformin, which lower insulin levels, can help reduce the likelihood of miscarriage. You definitely have findings that need to be reconciled with your clinical outcomes, and it may be that something can be identified that can be addressed with your next pregnancy. Talk to your doctor about that.