How to know if you have an underactive thyroid gland

What happens when your thyroid isn’t producing enough hormones? It can lead to a common condition called hypothyroidism, mostly in women. The symptoms show up subtly as fatigue, weight gain, brain fog and hair loss, and Dr. Bhanu Iyer, MD, an endocrinologist at Atlantic Health, says these issues are often connected and caused by an underactive thyroid gland.

“Thyroid hormones drive your metabolism, which is the speed that your body transforms the foods you eat into energy,” says Dr. Iyer. “An underactive thyroid not only affects your energy level, but impacts your heart, brain, skin, muscles, digestion, reproductive system and nearly every organ in your body.”

What exactly is the thyroid and hypothyroidism?

The thyroid is a small, butterfly-shaped gland in your neck and its role in your body is enormous. When this gland doesn’t produce enough thyroid hormones, it slows down all the body’s systems, leading to hypothyroidism.

Although this medical condition is quite common—in fact, eight to 10 times more common in women than in men—for most American adults, hypothyroidism can be effectively managed with a thyroid hormone supplement medication. However, if left undetected, it can become severe and, in rare cases, life-threatening.

“Hypothyroidism is more common in older women, particularly during the late menopausal transition and post-menopause years,” says Dr. Iyer. “However, identifying hypothyroidism is critical in women of reproductive age because untreated disease can cause infertility, miscarriage and adverse pregnancy outcomes.”

Common symptoms of hypothyroidism

An underactive thyroid gland can cause a wide range of symptoms that often don’t seem obvious or connected. Here are a few of the warning signs:

Fatigue or constant tiredness
Weight gain or difficulty losing weight
Constipation or bloating
Dry skin
Hair loss
Brittle nails
Feeling cold
Brain fog or slowed thinking

In more severe cases, symptoms may include:

Slow heart rate
Shortness of breath
Swelling in the legs or face
Loss of the outer portion of the eyebrows

How to test for hypothyroidism

There’s no need to start with a specialist; just talk to your primary care doctor about your symptoms. Diagnosing hypothyroidism starts with a simple blood test called a thyroid-stimulating hormone test or TSH. It is part of routine blood work, especially during pregnancy.

“If a person’s TSH level is abnormal, additional bloodwork can test thyroid hormone levels and antibodies,” says Dr. Iyer. “The majority of patients with hypothyroidism have positive thyroid antibodies, depending on the specific antibody tested and the population studied.”

How is hypothyroidism treated and managed?

The most common way to treat an underactive thyroid involves a daily medication to replace hormones your thyroid can no longer make. This is known as thyroid hormone replacement therapy and the dose is based on your blood test results, weight and severity of symptoms.

According to Dr. Iyer, hypothyroidism is one of the most treatable hormonal conditions. In fact, most people can manage it with the help of their primary care provider. And for those with complex health issues or at high risk of severe symptoms, it’s manageable with the help of an endocrinologist.

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Published: January 23, 2026

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