Connection between Hypothyroidism and PCOS

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Hypothyroidism is a state in which the thyroid gland does not make enough thyroid hormone. Many suspect hypothyroidism is related to polycystic ovary syndrome (PCOS), ovarian enlargement and cyst formation. A recent study investigated this hypothesis. It included 26 patients with untreated hypothyroidism who had polycystic (n=10) or normal-appearing (n=16) ovaries and 20 euthyroid controls. All subjects were given a battery of hormonal tests including basal serum total testosterone, free testosterone, androstenedione, dehydroepiandosterone-sulfate (DHEAS), prolactin, estradiol, luteinizing hormone, follicle-stimulating hormone (FSH), free triiodothyronine (FT3), free thyroxine (FT4), and thyroid-stimulating hormone (TSH).  Cortisol, 11-deoxycorticosterone and 17-hydroxyprogesterone (17-OHP), a progesterone derivative were also measured. Results from the hormone tests were compared with ovarian volumes.

Thyroid Hormones, PCOS and the Reproductive System

Thyroid hormones have various effects on the reproductive system of the human female. Alteration in thyroid function, particularly hypothyroidism, can cause ovulatory dysfunction and lead to impaired female fertility.  Hypothyroidism and PCOS are often accompanied by increased serum free testosterone, luteinizing hormone (LH) and high cholesterol. When the ovaries of hypothyroid women with PCOS are viewed with an ultrasound an increase in ovarian volume and the appearance of bilateral multicystic ovaries are often visible. When thyroid hormone replacement therapy is initiated, in addition to stabilizing thyroid hormone levels, ovarian cysts regress and ovarian volume is reduced.

Thyroid Hormone Replacement, Estradiol and the Androgens

In the current study a significant improvement in serum hormone levels occurred after thyroid hormone replacement therapy. Serum FT3 and FT4 levels increased whereas serum TSH, prolactin, estradiol, free testosterone and total testosterone levels decreased. The serum DHEAS levels of patients with polycystic ovaries remained high, and there was no overall change in serum cortisol, 17OHP and 11DOC levels. Improvement in the menstrual cycle occurred in 18 women. Serum total testosterone concentrations were significantly higher in hypothyroid patients without polycystic ovaries, and thyroid hormone replacement therapy achieved a significant reduction in total and free testosterone levels.

Thyroid Hormone Replacement and Menstrual Irregularities

Hypothyroid women commonly suffer from menstrual irregularities and impaired fertility attributed to annovulation and/or luteal phase defect. The present study showed that the women with hypothyroidism (with or without polycystic ovaries) had significantly larger ovaries when compared with controls, suggesting that thyroid dysfunction has a profound effect on ovarian size, and may also produce ovarian cysts.

Research in animals has shown that hypothyroidism causes collagen deposition within the ovarian intracellular matrix. In humans, hypothyroidism is characterized by deposition of mucopolysaccharides (hyaluronic acid and chondroitin sulfate) within the connective tissue of various organs. While additional collagen in the lips or to reduce the appearance of wrinkles can be a good thing, increased collagenic material in the ovaries creates problems with ovarian function and may dysregulate hormone synthesis.

Reproductive Hormone changes in Hypothyroid Women

The study showed that although the overall basal serum androgen level of patients with hypothyroidism tended to be higher, only the difference in total testosterone was statistically significant. Hypothyroid patients with polycystic ovaries had significantly higher serum DHEAS and free testosterone but lower androstenedione levels.

Achieving normal thyroid levels after replacement therapy decreased overall serum prolactin, E2, total and free T levels (but not androstenedione and DHEAS values) significantly compared to pre-treatment. Resumption of regular menses occurred in 50% of PCOS and 81% of non-PCOS patients after thyroid levels had been normalized. Additionally, the polycystic appearance of the ovaries disappeared in all patients after thyroxine treatment. These findings indicate that the PCOS-like appearance of the ovaries can be caused by primary hypothyroidism. A decrease in ovarian volume and resolution of ovarian cysts should be expected after euthyroidism has been achieved with thyroid hormone replacement therapy.


Sergei Avdiushko MBA, PhD has extensive experience in the emerging field of salivary diagnostics. He has developed diagnostic tests and assays for hormones and viral markers using a variety of methods. He has over 20 years of experience as a scientist in academia and more recently, several years in the biotech industry. Dr. Avdiushko holds a PhD in Biochemistry from the Biochemistry Institute in Moscow and an MBA from the University of Kentucky. Dr. Avdiushko has authored over 30 publications on plant pathology, immunology, disease resistance, lipid metabolism, and clinical research in peer-reviewed journals.


  1. i have pcos and hypothyroid…………u are supposed to eat spinach and kale and peanuts in pcos…………….but totally avoid them in hypothroid…………………i am confused whether to eat them or not,…………………pleaseeeee HELP

    • Anju,

      A partial response since I am not the author of the article: for hypothyroid you should consider increasing your iodine intake. Please ask your doctor about how much. The author of the article will respond the the rest of your question.

      Best wishes,

      • I have hypothyroidism (Hoshimotos)My thyroid specialist told me to never take iodine supplements. I was on synthroid medications taking natural thyroid vitamins and such I had researched and bought over internet but none helped. Even a leading heart healthy supplement I was taking had iodine in it! I stopped taking them. I thought maybe my iodine was low because I’d been using pink sea salt for 20 years or so. I was having no luck on 112 MGS of Levothyroxine So I asked my doctor if we could double up on Wed and Sundays. So I did it seemed ok for a while then my thyroid level went down below normal again. So I asked if we could get off the generic that my insurance company paid for with co-payment. I then got on LEVOXYL 112 MCG had to pay for out of my own pocket for few months Doctor finally sent request for the non generic Levoxyl they approved because my previous blood tests showed it was doing me no good at all. My Thyroid went up to normal very quickly I still double up on wed/Sun but no more anxiety attacks that were being caused by thyroid. I also asked doctor for blood tests for Vitamin B3 another panic attack and anxiety causer if your low no surprise I was very low so she put me on 50,000 mg once a week vitamin form. I go again next month for blood tests. I”m 66 years old and hanging in there as best I can other than thyroid problems all else is ok…except for weigh gain of course…

  2. also im suffering from weakness ,my hemoglobin -10.9 and glucose -81,..suggest for curing become healthy.

  3. I m patient of pcos and thyroid.. I’m gaining weight and heavy bleeding during menstruation. suggest treatment or advice. thank-you

    • For PCOS consider a clean, organic diet. Avoid gluten, that helps for both PCOS and thyroid. For thyroid, see the website or Facebook page ThyroidChange. They have a lot great articles on the topic.

  4. My daughter has a thyroid condition she is 13 years old but she is having heavy periods she also has a nexplanon impanted in her arm and that is not helping? I don’t know what to do.

  5. Anne Marie,

    I am so sorry for your struggles. There is a strong connection between autoimmune thyroid diseases and PCOS. Do you have Graves’ disease?

    If you have Graves’ disease which is an autoimmune disease that stimulates the thyroid gland and PCOS, the rash may be a result of the autoimmune process.

    I am a patient advocate for and am not a doctor, but I know that some patients see a decrease in allergies after being treated for their thyroid disease. Perhaps, it is all related.

    Is your doctor doing anything to manage your hyperthyroidism?

  6. Can someone please help I have hyperthyroidism and pocs but every month coming up to my period I come out in hives for around 2 weeks but my endocrinologist reckons that no way possible my rash -the pocs and my hyperthyroidism are related well I know it is they all started at the same time 9 years ago but im still not being treated as he says he doesn’t know what is causing my constant up down thyroid levels I also have thyroid nodules can anyone give me any advice im in the uk and havent been able to work for 9 yrs as I never sleep nor am I offered any sedative im 31 and never been pregnant im at my wits end dont think I can take much more it s totally ruined my life thanks for reading

  7. The only reason is that replacing more than one thyroid hormone requires a lot of data and clinical trials that are still to be performed and validated.

  8. Imagine the improvement if they also had triiodothyronine with the thyroxine (as in a Natural Desiccated Thyroid Medication)! Not enough study’s done on the difference between T4 only medications, and T3/T4 combo’s. If your thyroid produces 5 different hormones (in different amounts, but your thyroid still produces it throughout the day), why would you only replace one?

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