5 Things Women With PCOS Should Know About Hypothryoidism

Polycystic ovary syndrome (PCOS) and thyroid problems are two of the most common—and perhaps overlooked—endocrine (hormonal) disorders in women. Although PCOS and hypothyroidism (low thyroid function) PCOS are very different, they share many features.

This article takes a close look at five important things people with PCOS should know about hypothyroidism. This includes knowing what is involved in the diagnosis of hypothyroidism and what is needed to avoid thyroid-related complications of PCOS.

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Hypothyroidism in Women With PCOS

Hypothyroidism, and in particular Hashimoto's thyroiditis, is more common in people with PCOS than in the general population. Hashimoto's is an autoimmune disorder in which the body attacks and damages the thyroid gland, leading to hypothyroidism.

A 2013 study from India found that 22.5% of women with PCOS had hypothyroidism compared to 8.75% of those without PCOS.

A 2015 study from the National Institutes of Health reported that 22.1% of women with PCOS had Hashimoto's thyroiditis compared to 5% of women without.


Hypothyroidism, and particularly the autoimmune disorder Hashimoto's thyroiditis, occurs in women with PCOS at a rate three to four times greater than in women without PCOS.

How Hypothyroidism Worsens PCOS

Hypothyroidism is known to affect the ovaries in a similar way as PCOS, causing the enlargement of the ovaries and the formation of cysts.

Hypothyroidism tends to worsen PCOS symptoms, including an increased risk of insulin resistance (the inability of the body to utilize insulin to control blood sugar) and type 2 diabetes.

Hypothyroidism can also increase the production of the male hormone testosterone (referred to as hyperandrogenism). This can increase the risk of PCOS-related symptoms like acne, male-pattern hair loss, and hirsutism (abnormal facial or body hair). Hyperandrogenism can also lead to irregular periods.

Too much testosterone can also interfere with the development of the follicles (the sacs in the ovaries where eggs develop) and prevents normal ovulation (the release of a mature egg).


Hypothyroidism can worsen the symptoms of PCOS, including increased insulin resistance, irregular periods, abnormal hair growth, and male-pattern baldness. It can also affect ovulation and the normal development of eggs.

How Hypothyroidism Complicates PCOS

Located in the base of your throat, the butterfly-shaped thyroid gland regulates the rate at which your body converts food to energy (referred to as metabolism). Thyroid hormones also help control your heart rate and influence your menstrual cycle and fertility.

If the thyroid gland works too slowly (hypothyroidism), your metabolism will slow down, resulting in weight gain. Weight gain is a central feature for many women with PCOS.

Hypothyroidism can also complicate PCOS, causing symptoms not typically seen with the disorder. This includes bradycardia (a slowed heart rate), facial swelling ("moon face"), and a goiter (an enlarged thyroid gland).


In addition to worsening the symptoms of PCOS, hypothyroidism can cause symptoms not commonly seen with PCOS. These include an abnormally slowed heart rate, facial "mooning," and a goiter (an enlarged thyroid gland),

Why Hypothyroidism Is Missed

Thyroid-stimulating hormone (TSH) is a hormone produced by the pituitary gland that regulates the release of the thyroid hormones T3 and T4.

Abnormally high TSH levels suggest that you may be hypothyroid. This is because the pituitary is working overtime in an effort to stimulate an underactive thyroid gland.

Even so, a high TSH on its own does not mean you have hypothyroidism. The diagnosis also requires a series of T3 and t4 tests as well as an anti-TPO test to check if you have an autoimmune thyroid disease like Hashimoto's.

Because hypothyroidism is often tricky to diagnose, it is commonly misdiagnosed in women with PCOS.


Hypothyroidism can be difficult to diagnose and may be missed in women with PCOS unless a complete diagnostic evaluation is performed. On its own, a high TSH level is not diagnostic of hypothyroidism.

Iodine Plays a Big Role

The thyroid must have iodine to make thyroid hormones. The main food sources of iodine include dairy products, chicken, beef, pork, fish, and iodized salt.

Keeping T3 and T4 production in balance requires the right amount of iodine. Too little or too much can cause or worsen hypothyroidism.

To this end, women with PCOS need to be extra aware of their iodine intake if they have been diagnosed with (or are at risk of) hypothyroidism. Doing so can minimize the impact of hypothyroidism, and, in turn, minimize the impact hypothyroidism may have on PCOS.


Women with PCOS and hypothyroidism need to be aware of their iodine intake to ensure they neither get too much nor too little. By better managing hypothyroidism, any effect it may have on PCOS can be minimized.


Hypothyroidism (low thyroid function) is common in women with PCOS. This includes an autoimmune form of the disease called Hashimoto's thyroiditis.

Hypothyroidism can not only worsen the symptoms of PCOS (including weight gain, irregular periods, and increased insulin resistance) but it can cause symptoms not commonly seen with PCOS. These include goiters (an enlarged thyroid gland), facial mooning, and bradycardia (an abnormally slow heart rate).

Hypothyroidism can be tricky to diagnose and is sometimes missed in women with PCOS. If it is diagnosed, hypothyroidism needs to be properly managed to minimize its impact on PCOS. This includes the proper dietary intake of iodine.

5 Sources
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  2. American Thyroid Association. Hypothyroidism: A booklet for patients and their families.

  3. Sinha U, Sinharay K, Saha S, Longkumer TA, Baul SN, Pal SK. Thyroid disorders in polycystic ovarian syndrome subjects: A tertiary hospital-based cross-sectional study from Eastern India. Indian J Endocrinol Metab. 2013;17(2):304-9. doi:10.4103/2230-8210.109714

  4. Arduc A, Aycicek Dogan B, Bilmez S, Imga Nasiroglu N, Tuna MM, Isik S, Berker D, Guler S. High prevalence of Hashimoto's thyroiditis in patients with polycystic ovary syndrome: does the imbalance between estradiol and progesterone play a role? Endocr Res. 2015;40(4):204-10. doi:10.3109/07435800.2015.1015730

  5. 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;24(11):2924-30. doi:10.1093/humrep/dep285

Additional Reading

By Angela Grassi, MS, RDN, LDN
 Angela Grassi, MS, RDN, LDN, is the founder of the PCOS Nutrition Center.