Have you ever felt like something in your body is just… off? Perhaps you’re constantly exhausted, no matter how early you go to bed. Maybe you've noticed hair thinning, unexplained weight gain, or skin that feels dry enough to crack. These symptoms can be confusing—and frustrating—especially when they don’t seem to have a clear cause.

What many people don’t realize is that all these problems can stem from a single source: your thyroid gland.

This small, butterfly-shaped gland in your neck is the master regulator of your metabolism. It produces hormones that control energy production, body temperature, digestion, heart rate, and even your mood. When your thyroid slows down—a condition known as hypothyroidism—your entire body shifts into “low-power mode,” and the symptoms can be surprisingly wide-ranging.

Millions of people have hypothyroidism without knowing it because the signs can be subtle at first and easy to blame on stress, age, or lifestyle. Today, we’re breaking down the top 15 signs of an underactive thyroid so you know exactly what to look for.
(Based on the expertise of Dr. Siobhan Deshauer.)

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👉 Key Takeaways

• What it is: Hypothyroidism occurs when the thyroid doesn’t produce enough hormones, slowing down essential bodily functions.

• Visible signs: Changes often show up in skin, hair, nails, or swelling in the face or neck.

• Hidden symptoms: Fatigue, mood changes, menstrual issues, and cold intolerance are common but often overlooked.

• Diagnosis & treatment: A simple blood test can diagnose the condition, and treatment with thyroid hormone replacement is highly effective.

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1. An Enlarged Thyroid (Goiter)

One of the clearest signs of thyroid trouble is a visible swelling at the base of the neck. When your thyroid can’t produce enough hormone, your brain increases the release of TSH (Thyroid Stimulating Hormone) to push the gland to work harder. Over time, this extra pressure can cause the thyroid to grow in size, forming a goiter.

A mild goiter may be barely noticeable, but a larger one can cause:

• difficulty swallowing

• voice changes

• tightness in the throat

• shortness of breath when lying down

If you ever notice swelling in your neck, especially one that seems to grow, you should speak with a healthcare provider promptly.

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2. Dry, Rough, Cracking Skin

Your skin depends on thyroid hormones to maintain a healthy barrier. When these hormones fall too low, your oil glands slow down dramatically. Without enough natural oils to lock in moisture, your skin becomes:

• rough

• flaky

• itchy

• cracked in a mosaic-like pattern

People often spend months trying different creams before realizing the problem isn’t the skin itself—it’s the thyroid behind it.

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3. Thickened Skin on Hands and Feet

Thyroid hormones help regulate how quickly your skin cells renew themselves. When this renewal slows, dead skin and keratin build up, especially on areas that experience pressure, like the palms and soles.

This can lead to:

• thick, stiff skin

• deep cracks

• painful callus-like patches

• a condition called palmar-plantar keratoderma

This sign often appears long before a diagnosis is made.

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4. Hair Loss and Thinning

Hair follicles are extremely sensitive to hormone changes. Hypothyroidism disrupts their growth cycle, causing hairs to enter a resting phase too early.

You may notice:

• overall thinning

• dry, brittle strands

• excessive shedding in the shower

• hairbrush full of loose hairs

Unlike typical pattern baldness, thyroid-related hair loss tends to be diffuse, affecting the entire scalp.

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5. Brittle, Splitting, or Thick Nails

Low thyroid hormone slows nail growth and disrupts nail structure. Nails may become:

• thick but fragile

• split easily

• dull and ridged

• vulnerable to separation from the nail bed (onycholysis)

This can be one of the earlier cosmetic signs of hypothyroidism.

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6. Thinning of the Outer Eyebrows

This classic sign—sometimes called the “Queen Anne sign”—refers to thinning or loss of the outer third of your eyebrows. This isn’t a cosmetic issue; it reflects a disruption in hair growth cycles related to low hormone levels.

If your eyebrows seem to be fading, especially towards the ends, your thyroid may be to blame.

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7. Puffy Face and Swelling Under the Eyes

Hypothyroidism leads to a buildup of a jelly-like substance called myxedema, which gathers in the skin and tissues. This causes swelling, especially around the eyes and cheeks.

Myxedema isn’t simply water retention—it's a true structural change in the tissue. The skin may feel doughy or unusually firm.

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8. A Swollen Tongue

This same myxedema can also infiltrate muscles, including the tongue. A swollen tongue can cause:

• snoring

• difficulty speaking clearly

• bite marks along the edges

• worsening sleep apnea

For some people, this symptom is the one that finally points them toward a thyroid evaluation.

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9. Numbness and Tingling in the Hands (Carpal Tunnel)

Swelling inside the wrist can compress the median nerve, leading to:

• tingling

• numbness

• burning

• wrist or hand pain

Interestingly, carpal tunnel syndrome can be one of the first signs of untreated hypothyroidism.

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10. Feeling Cold All the Time

Hypothyroidism slows your metabolism, meaning your body produces significantly less heat. As a result, many people:

• wear sweaters in warm weather

• sleep in extra layers

• have cold hands and feet year-round

If you constantly feel chilly while others are comfortable, your thyroid could be underperforming.

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11. Yellow-Orange Skin (Carotenemia)

Beta-carotene from foods like carrots, squash, and sweet potatoes is normally converted into vitamin A. But in hypothyroidism, this conversion slows dramatically.

This leads to a buildup of pigment in the skin, especially:

• on the palms

• on the soles

• around the nose

Unlike jaundice, the whites of the eyes remain normal in carotenemia.

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12. Depression, Brain Fog, and Mood Changes

Thyroid hormones profoundly influence your brain chemistry. Low levels can cause:

• decreased serotonin and dopamine

• slowed processing speed

• poor concentration

• emotional flattening

• forgetfulness

For this reason, physicians often check thyroid function during mental health evaluations.

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13. Heavy or Irregular Menstrual Cycles

Thyroid hormone interacts closely with reproductive hormones. When levels drop, you may experience:

• heavier bleeding

• longer periods

• shorter cycles

• fertility challenges

• worsened PMS symptoms

This is one of the reasons undiagnosed hypothyroidism is sometimes discovered during fertility testing.

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14. Chronic Fatigue

This isn’t just ordinary tiredness—it’s a deep, lingering exhaustion. Even a full night’s sleep may not help. You may find yourself struggling to:

• concentrate

• stay awake during the day

• perform simple tasks

• exercise without feeling drained

Fatigue is one of the most universal signs of hypothyroidism.

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15. Unexplained Weight Gain and Constipation

Since thyroid hormones regulate metabolism and digestion, low levels slow down both.

This means:

• you burn fewer calories

• you gain weight easily

• bowel movements become infrequent or difficult

Even small hormone imbalances can result in noticeable changes on the scale.

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⚙️ What to Do Next

If several of these signs sound familiar, the next step is simple: talk to your healthcare provider. Diagnosis usually involves a blood test that measures your TSH (and often free T4).

If the results confirm hypothyroidism, treatment is straightforward. The most common therapy is levothyroxine, a synthetic form of thyroid hormone that restores hormone levels to normal.

With proper treatment, many symptoms slowly fade, and most people regain their energy, mood, physical comfort, and quality of life.