The link between PCOS and Hypothyroidism: The OAT axis.


If you have been diagnosed or suspect you have PCOS, this could be a big eye opener for you.

There have been several research studies clinically linking Polycystic Ovary Syndrome (PCOS) and subclinical hypothyroidism (not yet full blown hypothyroidism, as in diagnosable through testing) (Ding, et al. 2018). Meaning, you may personally experience the symptoms but your blood tests don't show enough of a irregularity to be diagnosed hypothyroid. Usually, it's common to see PCOS presenting with metabolic and cardiovascular conditions, such as insulin resistance, however, autoimmune thyroid disease has been reported in <40% of diagnosed PCOS individuals (Romitti, et al. 2018). Autoimmune thyroid (hashimoto's) and hypothyroid are different in how they are caused and treated, but the symptoms are the same.


If you are experiencing these symptoms, autoimmune conditions should be ruled out: symptoms “such as poor ability to tolerate cold, tiredness, constipation, depression, and weight gain” as they relate to thryoid function (Ding, et al. 2018). Romitti, et al. (2018) suggests dysregulation of the hypothalamic-pituitary-ovary(gonadal) axis (HPG/HPO) as one of the mechanisms underlying PCOS. Potentially this is in addition to autoimmune causes with antiovarian auto-antibodies - this is not well supported, but more likely still causes immune dysregulation. Basically, the organs and glands which control a lot of bodily mechanics aren't communicating with each other clearly because; a) a gland or its product is not working appropriately or b) a gland is under immune attack = not able to do its job.


Now, how is thyroid connected to PCOS you ask..?

Ding, et al. (2018) and Romitti, et al. (2018) both suggest the oestrogen ‘dominance’ present in PCOS over stimulates the immune system and heightens the risk for autoimmune conditions. In more direct relationships, Lam (2020) discusses the OAT (ovarian-adrenal-thyroid) axis which controls the connection between your reproductive hormones, stress response and thyroid hormones. This axis is relatively unexplored as of now, however Lam suggests the imbalance in reproductive hormones (i.e. the ovaries and relative oestrogen dominance seen in PCOS) affects the adrenals and thyroid. He suggests the mechanisms include increased thyroid-binding proteins (= less active thyroid hormone), and interfering (stimulating) with cortisol release, cortisol-binding protein, and (inhibiting) metabolism, which are supported in the research papers (Santin & Furlanetto, 2011; Yates, 2010). This directly interfers with your thyroid function and stress response = a slower metabolism and higher chances of weight gain due to how cortisol and insulin interact.


More independent research is needed to clarify (with data) the OAT axis and its implications, however the link between PCOS and hypothyroidism has been demonstrated over and over. Imbalances anywhere in the body affect other organs/systems so it is reasonable to suggest such organs communicate frequently.


If you have any questions/comments, please leave them below and I'll do my best to answer them.



Bonus note:

There are different immune responses associated with different autoimmune thyroid conditions... though skip this part if you don't need the details.

Th1-mediated autoimmunity is associated with Hashimoto’s, and relating to PCOS - androgens that are elevated in PCOS reduce areas of the immune system yet enhance T suppressor cell activity and Th1 response (Romitti, et al. 2018).

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