PCOS and Thyroid Health

PCOS & Thyroid Health

Fiona has PCOS herself and she commonly works with women who have PCOS and suboptimal thyroid hormone levels. I knew she would be the perfect person to invite to write a guest post about this important connection between PCOS and thyroid health.

Written by Fiona McCulloch, ND

Polycystic ovarian syndrome (PCOS) is the most common reproductive disorder, affecting up to 12 percent of all women. It is a disorder with many different faces, and it causes great emotional and physical distress to the millions of women worldwide who suffer from it.

2 of the 3 following criteria are required for a diagnosis of PCOS (as defined by the Rotterdam Criteria):

1) Anovulation or Irregular Periods

2) Hyper-androgenism/elevated male hormone levels


Clinical hyper-androgenism: adult acne, hirsutism (a male pattern of body or facial hair), or hair loss (androgenic alopecia)

3) Polycystic appearing ovaries on ultrasound, containing multiple small follicles

Women with PCOS are at risk for infertility and early pregnancy loss. Many are overweight, find it difficult to lose weight, and suffer with fatigue, depression and anxiety. There’s a significant overlap of symptoms between PCOS and Thyroid Disease, despite the fact that they are two very different conditions.

Is there an actual relationship between PCOS and thyroid function? Let’s take a look at the research to learn more about this important connection.

PCOS, Thyroid, and Insulin Resistance

First and foremost, it is known that insulin resistance is a major component of PCOS, and 50-70% of those suffering from it have high insulin levels or impaired blood sugar regulation. It’s important to note that insulin resistance develops many years before diabetes, so the most common tests for diabetes don’t often pick it up. Insulin resistance is caused by a variety of factors, including genetics, weight, diet, and lifestyle.

Insulin is a hormone that signals muscle and fatty tissue to take up glucose from the bloodstream and to store it as fat or energy. When the body tissues are “resistant” to insulin, the pancreas simply makes more insulin to compensate and to keep the blood sugar levels controlled. As such, a woman with PCOS will often have much higher insulin levels in her blood than normal.

With PCOS, even though other tissues in the body are resistant to insulin, for some reason the ovaries and pituitary gland remain very sensitive to it. High insulin levels cause the pituitary gland to make too much luteinizing hormone (LH), and too much LH causes the overproduction of testosterone, thus hindering ovulation.

As part of a vicious cycle, the high testosterone in PCOS sparks even more insulin resistance.[1] You can get a general idea of how high levels of insulin contribute to the overall picture of PCOS as a result: the higher the insulin, the more severe hormonal dysregulations become.

Interestingly, research suggests that low thyroid function aggravates insulin resistance in PCOS.[2]

Subclinical Hypothyroidism: Is it related to PCOS?

On average, women with PCOS have higher TSH levels and are also more likely to have subclinical hypothyroidism when compared to age-matched controls without PCOS.[3]

When it comes to defining subclinical hypothyroidism itself, there is great controversy which I’m sure that many readers of this blog will be well aware of. Several studies have suggested a lower cut off than the conventional 4-5 miU/L to define subclinical hypothyroidism. The National Academy of Clinical Biochemistry (NACB)’s laboratory guidelines state that >95% of rigorously screened normal euthyroid volunteers have serum TSH values between 0.4 and 2.5 mIU/L.[4]

There is little research on the use of FT3 and FT4 for the diagnosis of subclinical hypothyroidism, but countless patients and clinicians have experienced that these markers are important correlations to overall wellness and energy levels. In my own naturopathic practice, I find it generally best to treat the patient’s signs and symptoms, as patients feel best at different “personal” ranges for thyroid markers. That being said, some evidence does suggest that women who have PCOS with a TSH out of a specific range may be at increased risk.

TSH levels and PCOS

A 2009 study looked at a group of 337 women with PCOS. All of the women were assessed for the key markers of PCOS, including hirsutism, acne, and menstrual irregularity.

What the researchers found was that the women who had the lowest levels of insulin resistance also had the lowest TSH values (under 2miU/L). Women with the highest TSH values tended to have the most severe insulin resistance. Interestingly, this was not related to weight: subclinical hypothyroidism caused insulin resistance in women in all weight categories.

The study concluded that a TSH above 2 miU/L was associated with insulin resistance in PCOS.

Another study on women with PCOS[5] found that those who had a TSH > or =2.5 mIU/L had a higher BMI, higher fasting insulin levels, higher total testosterone, and decreased sex hormone-binding globulin concentrations in comparison with women with a TSH <2.5 mIU/L.

As such it appears that for women with PCOS, an optimal TSH range may be below 2-2.5 mIU/L.

Again, the research existing on this topic is focused on TSH, but it is also highly likely that an optimal range exists for FT3 and FT4 in PCOS. In my practice, I have found that values at the top 1/3 to 1/4 of the range may provide benefit for some women with PCOS.

Sex Hormone Binding Globulin, Thyroid and PCOS

Changes in thyroid function can also influence levels of sex hormone binding globulin (SHBG). This compound serves to bind up the male hormones in the blood, and when levels are low, male hormones run rampant in the body, producing all of the unpleasant symptoms of PCOS. Typically in PCOS, high levels of insulin push down the SHBG, leaving androgenic hormones free to create problems.

Thyroid hormones increase the levels of SHBG.[6] A deficiency in thyroid hormones will make androgenic symptoms such as hair loss, acne, and hirsutism worse.

Ovarian Volume and Ovarian Cysts in Hypothyroidism

Interestingly, hypothyroidism itself may induce a PCOS-like picture. Hypothroidism increases the size of the ovaries and promotes cyst formation, and collagen deposits are found within the ovaries of animals with hypothyroidism. Interestingly, in humans, hypothyroidism causes the deposit of mucopolysaccharides within various organs. Material deposited in the ovaries hampers ovarian function and hormone synthesis, resulting in disrupted menstrual cycling. The “cysts” of PCOS are actually follicles that have not ovulated, having undergone partial development. As such, the disruption of ovulation by hypothyroidism may also produce similar cysts.

A 2011 study[7] compared two groups of women with hypothyroidism—one group with polycystic ovaries and the other with normal ovaries—to a group of women with normal thyroid function. The researchers discovered that the hypothyroid women had larger ovaries. Providing thyroid hormone replacement therapy reduced the size of the ovaries in both groups of hypothyroid women, and improved TSH, FT3 and FT4, prolactin, estradiol, free testosterone and total testosterone levels.

Interestingly, in all hypothyroid women in this study, the polycystic ovary appearance completely disappeared when thyroid function was restored. Although many of the women experienced improved menstrual regularity, 50% of the women with polycystic ovaries still did not begin to cycle regularly.

As such, we can see that hypothyroidism can create an ovarian condition similar to PCOS, but the two conditions can also co-exist.

Autoimmune Thyroiditis and PCOS

Autoimmune thyroid disease, also known as Hashimoto’s thyroiditis, is the leading cause of hypothyroidism in women of reproductive age. There is a clear correlation between Hashimoto’s thyroiditis and PCOS.

A 2012 study[8] found that women with PCOS had a 65% increase in thyroid peroxidase antibodies, and a 26.6% increase in the incidence of goiter, when compared to age-matched subjects.

Another 2013 analysis[9] found that in a total of 6 studies involving 1605 women, there was an increased prevalence of autoimmune thyroiditis, increased serum TSH, increased anti TPO antibodies, and anti TG antibodies in women with PCOS when compared to control groups.

In addition to the higher incidence of autoimmune thyroid disease in women with PCOS, a recent study[10] showed that women suffering with PCOS-related infertility who also had high anti-TPO levels were significantly more likely to be resistant to Clomid. The study went on to conclude that autoimmune thyroid disease is associated with poor treatment response in infertile women who suffer from PCOS.

The Bottom Line on PCOS and Thyroid Function

At this point, one thing is absolutely clear: all women with PCOS should have their thyroids evaluated thoroughly (TSH, FT3, FT4, Anti TPO, Anti TG). Thyroid health has a profound impact on the pathology of PCOS, affecting all aspects of the disorder. In my practice, I commonly work with women who have PCOS and “suboptimal” thyroid hormone levels, and I have found that correcting subclinical hypothyroidism is key to improving overall hormonal and metabolic health.

Some patients with PCOS require thyroid hormone replacement therapies, but there are also PCOS patients with mild thyroid hypofunction or Hashimoto’s who benefit greatly from therapies such as adrenal support, thyroid specific nutritional supplements, and dietary changes to reduce autoimmunity.

As a Naturopathic Doctor as well as a woman with PCOS, I have firsthand experience with the results that can be achieved via lifestyle change, a diet that lowers inflammation and insulin levels, and supplements/herbs that address hormone regulation. These simple changes work together to create a truly effective reversal of this disorder.

When it comes to both thyroid conditions and PCOS, each patient is truly unique in her needs. Our hormonal systems are complex and intertwined, and doctors should look at the specific relationships that exist in each and every patient to create a plan that helps to restore optimal metabolic and hormonal health.

About Dr. Fiona McCulloch

Dr. Fiona McCulloch is a board certified Naturopathic Doctor who has been in practice since 2001 in Toronto, Canada. Fiona is the founder and owner of White Lotus Naturopathic, a busy clinic specializing in women’s health, endocrinology and fertility. Her clinical focus is on the treatment of fertility and hormonal conditions and she is an avid writer and researcher, developing naturopathic treatment protocols for hormonal concerns based on the most current evidence.

READ NEXT: Polycystic Ovary Syndrome (PCOS) or Hypothyroidism?


  1. Dunaif A. Insulin resistance and the polycystic ovary syndrome: mechanism and implications for pathogenesis. Endocr Rev 1997;18:774-800.
  2. Mueller A, Schöfl C, Dittrich R, Cupisti S, Oppelt PG, Schild RL, Beckmann MW, Häberle L. Thyroid-stimulating hormone is associated with insulin resistance independently of body mass index and age in women with polycystic ovary syndrome. Hum Reprod. 2009 Nov;24(11):2924-30.
  3. Janssen OE, Mehlmauer N, Hahn S, Offner AH, Gärtner R. High prevalence of autoimmune thyroiditis in patients with polycystic ovary syndrome. Eur J Endocrinol. 2004 Mar;150(3):363-9.
  4. NACB: Laboratory Support for the Diagnosis and Monitoring of Thyroid Disease. Laurence M. Demers, Ph.D., F.A.C.B.and Carole A. Spencer Ph.D., F.A.C.B.
  5. Dittrich R, Kajaia N, Cupisti S, Hoffmann I, Beckmann MW, Mueller A. Association of thyroid-stimulating hormone with insulin resistance and androgen parameters in women with PCOS. Reprod Biomed Online. 2009 Sep;19(3):319-25.
  6. Selva DM, Hammond GL. Thyroid hormones act indirectly to increase sex hormone-binding globulin production by liver via hepatocyte nuclear factor-4alpha. J Mol Endocrinol. 2009 Jul;43(1):19-27.
  7. Muderris II, Boztosun A, Oner G, Bayram F. Effect of thyroid hormone replacement therapy on ovarian volume and androgen hormones in patients with untreated primary hypothyroidism. Ann Saudi Med. 2011 Mar-Apr;31(2):145-51.
  8. Kachuei M, Jafari F, Kachuei A, Keshteli AH. Prevalence of autoimmune thyroiditis in patients with polycystic ovary syndrome. Arch Gynecol Obstet. 2012 Mar;285(3):853-6.
  9. Du D, Li X. The relationship between thyroiditis and polycystic ovary syndrome: a meta-analysis. Int J Clin Exp Med. 2013 Oct 25;6(10):880-9.
  10. Ott J, Aust S, Kurz C, Nouri K, Wirth S, Huber JC, Mayerhofer K. Elevated antithyroid peroxidase antibodies indicating Hashimoto’s thyroiditis are associated with the treatment response in infertile women with polycystic ovary syndrome. Fertil Steril. 2010 Dec;94(7):2895-7.

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About Dana Trentini

Dana Trentini founded Hypothyroid Mom October 2012 in memory of the unborn baby she lost to hypothyroidism. This is for informational purposes only and should not be considered a substitute for consulting your physician regarding medical advice pertaining to your health. Hypothyroid Mom includes affiliate links including the Amazon Services LLC Associates Program.


  1. I was diagnosed with PCOS when I was 7 years ago. I have 3 kids from 2 pregnancies (twins) and since the last baby (2 yrs old) I’ve been far more exhausted even on the weekends when I sleep 9-11 hours. This past January my primary care doctor noticed my thyroid and had an ultrasound done because after having the flu I made a comment about how I sleep on the couch so I’m partially sitting whenever I’m congested because it’s easier to breath and cough. Turns out I have an enlarged thyroid with nodules. TSH came back at 0.79 and T4free was 0.94. She said it was working find. However during all of that I got chronic laryngitis and lost my voice for over 2 months. I just recently got it back in the middle/end of March. The ENT couldn’t explain it and has me coming back in in 8 weeks. Also, my periods had gotten very irregular and heavier even while I was on Metformin (which I hate). A1c test just came back as normal.

    Basically my doctors keep saying PCOS but no one seems concerned with why my thyroid is enlarged. And I keep feeling like all those symptoms happening with all of this and the dry skin in the past 2 years is more than just my PCOS. Do I sound crazy?

  2. Wykina Thomas says

    My Girlfriend just found out She has a big Mass on her low Thyroid have to see a endocrinologist but its so High with no Insurance

  3. Hi Dana,
    My question is what if the thyroid blood testing is within the normal range. Dr is stating PCOS and wants to put me on metformin 4x a day. my tsh is .54 which is on the lower end.But my prolactin is elevated! If you have any suggestions on testing ?

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