Hypothyroidism vs. PCOS: Key Differences & Symptoms Explained

Feeling exhausted all the time? Struggling with irregular periods, unexplained weight gain, or changes in your energy levels? You’re not alone. Many women experiencing these symptoms wonder whether hypothyroidism or polycystic ovary syndrome (PCOS) could be the cause.

Both conditions can cause fatigue, weight gain, hair changes, and menstrual irregularities, making them difficult to tell apart. The good news is that key differences in symptom patterns and diagnostic testing can help point to the right diagnosis and treatment.

In this guide, we’ll explain how PCOS and hypothyroidism compare, where symptoms overlap, and what tests doctors use to determine what’s really behind your symptoms.

Hypothyroidism vs. PCOS: What’s the Difference?

At first glance, PCOS and hypothyroidism can look surprisingly similar. Both are hormone-related conditions that can affect your menstrual cycle, energy levels, weight, and overall well-being.

But what’s happening behind the scenes is actually quite different.

PCOS is primarily a reproductive and metabolic condition. It’s associated with elevated androgen levels, insulin resistance, and irregular ovulation. These hormonal changes can affect fertility, menstrual cycles, skin health, and metabolism.

Thyroid disorders occur when the thyroid gland produces too much or too little thyroid hormone. This article focuses on hypothyroidism, which occurs when the thyroid gland does not produce enough thyroid hormone. Because thyroid hormones help regulate metabolism and energy production, low levels can affect multiple body systems.

In general, PCOS primarily affects reproductive hormones and insulin regulation, while hypothyroidism primarily affects metabolism and energy regulation. However, both conditions can cause similar symptoms, including fatigue, weight gain, and irregular periods.

Research suggests that women with PCOS may be more likely to develop hypothyroidism than women without PCOS. A 2023 study published in Frontiers in Endocrinology found a significant association between PCOS and thyroid dysfunction, making it important to evaluate for both conditions when symptoms overlap.

Hormonal Imbalance Symptoms: Is It Hypothyroidism, PCOS, or Something Else?

When hormones are out of balance, your body has a way of letting you know. The challenge is that many hormone-related conditions can cause very similar symptoms.

Common signs of hormonal imbalance in women include:

• Irregular or missed periods
• Unexplained weight changes
• Fatigue that doesn’t improve with rest
• Mood changes, including anxiety, depression, or irritability
• Hair thinning or hair loss
• Acne or other skin changes
• Difficulty concentrating or brain fog

Because these symptoms can show up in several different conditions, blood work and a thorough evaluation are often needed to figure out what’s really going on.

Hypothyroidism Symptoms in Women

When people compare PCOS and thyroid problems, they’re usually talking about hypothyroidism, also known as an underactive thyroid.

The thyroid is a small gland in the front of the neck that helps regulate metabolism, energy production, body temperature, and other essential functions. When it doesn’t produce enough thyroid hormone, many of the body’s processes begin to slow down.

According to the American Thyroid Association, women are five to eight times more likely than men to develop thyroid problems.

Common hypothyroidism symptoms in women include:

• Persistent fatigue or low energy
• Feeling cold when others are comfortable
• Dry skin and brittle nails
• Constipation
• Gradual, unexplained weight gain
• Heavy or irregular menstrual periods
• Hair thinning, including around the outer edges of the eyebrows
• Difficulty concentrating or brain fog
• Depression or low mood

Because symptoms often develop gradually, it’s easy to blame them on stress, burnout, aging, or simply having a lot on your plate.

If several of these symptoms sound familiar, thyroid testing may help connect the dots.

PCOS and Hypothyroidism Symptoms: What Overlaps and What Doesn’t

Because PCOS and hypothyroidism share so many symptoms, it helps to look at where they overlap and where they start to differ.

Both PCOS and hypothyroidism may cause:

• Irregular periods
• Weight gain
• Fatigue
• Hair thinning
• Fertility challenges
• Mood changes

That said, certain symptoms tend to point more strongly toward one condition than the other.

Signs That May Point Toward PCOS

• Excess facial or body hair
• Persistent acne
• Oily skin
• Male-pattern hair thinning
• Elevated androgen levels
• Insulin resistance
• Darkened skin patches (acanthosis nigricans)

Signs That May Point Toward Hypothyroidism

• Sensitivity to cold temperatures
• Dry skin
• Constipation
• Brittle nails
• Diffuse hair thinning
• Slower metabolism

Adding to the confusion, hypothyroidism can sometimes cause ovarian changes that look like polycystic ovaries on an ultrasound. However, polycystic-appearing ovaries alone do not confirm a PCOS diagnosis.

Because hypothyroidism can mimic several PCOS symptoms, healthcare providers often evaluate thyroid function during a PCOS workup.

How Doctors Tell Hypothyroidism and PCOS Apart (Tests and Diagnosis)

Since symptoms alone don’t provide the full picture, doctors usually rely on a combination of your symptoms, medical history, physical exam, and laboratory testing.

Tests for Hypothyroidism

Your healthcare provider may order:

• TSH (thyroid-stimulating hormone): Usually the first test used to assess thyroid function
• Free T4: Measures the amount of available thyroid hormone in the blood
• Thyroid antibodies: May help identify autoimmune causes of hypothyroidism, such as Hashimoto’s thyroiditis

Together, these tests help determine whether your thyroid is functioning properly and whether an autoimmune condition may be contributing to your symptoms.

Tests for PCOS

A PCOS evaluation may include:

• Testosterone and other androgen levels
• LH and FSH hormone testing
• Glucose and metabolic testing
• Insulin resistance assessment
• Pelvic ultrasound when appropriate

Unlike hypothyroidism, there is no single test that confirms PCOS. Diagnosis is based on a combination of symptoms, hormone levels, and reproductive findings.

Because hypothyroidism can cause irregular periods, weight gain, and fertility issues, thyroid testing is often included in a comprehensive PCOS evaluation.

Can You Have Both PCOS and Hypothyroidism?

Yes, and it’s more common than many people realize.

PCOS and hypothyroidism can occur together, and hypothyroidism appears to be more common among women with PCOS than among women without it.

When both conditions are present, symptoms can become more pronounced. Fatigue may worsen, weight management may become more difficult, and fertility challenges can become more complex.

The good news is that both conditions are highly treatable. Once the underlying causes are identified, treatment can often lead to noticeable improvements in symptoms, energy levels, and overall quality of life.

If you’ve already been diagnosed with PCOS, screening for hypothyroidism may be worth discussing with your healthcare provider.

Likewise, if you have hypothyroidism and begin experiencing symptoms such as excess hair growth, worsening acne, or increasingly irregular cycles, it may be worth discussing a PCOS evaluation.

When to See an Endocrinologist

Your primary care provider or OB-GYN can often manage straightforward cases of either condition. However, certain situations benefit from specialist evaluation. 

In some situations, it may make sense to bring in an endocrinologist, especially if:

• Your symptoms persist despite treatment
• You have both PCOS and hypothyroidism
• You’re experiencing fertility challenges
• Your hormone levels are difficult to stabilize
• Your diagnosis remains unclear
• You have questions about long-term management

An endocrinologist specializes in hormonal disorders and can help coordinate care and develop a treatment plan when multiple endocrine systems are involved.

Frequently Asked Questions