Hypothyroidism Symptoms: How an Underactive Thyroid Shows Up in Your Skin, Hair, and Body

You're exhausted no matter how much you sleep. Your skin is dry and flaky, your hair feels thinner, and you're cold when everyone else is comfortable. It's easy to blame stress, aging, or winter weather, and often that's exactly what it is. But this same cluster of changes can also be your thyroid quietly slowing down.

Hypothyroidism, or an underactive thyroid, develops slowly and its early symptoms are mild and easy to miss. The good news: it's common, it's diagnosed with a simple blood test, and it's very treatable. Here's what the symptoms actually look like, including the skin and hair clues, and when it's worth getting checked.

What is hypothyroidism?

Hypothyroidism means your thyroid, a small gland at the front of your neck, isn't making enough thyroid hormone. That hormone sets the pace for your metabolism, so when levels drop, many of your body's systems run slower than they should.

It's more common than most people realize. According to the NIH, nearly 5 out of 100 Americans ages 12 and older have hypothyroidism, though most cases are mild. It's far more common in women than in men, and the risk rises after age 60. Because symptoms come on gradually over years and are often nonspecific, many people live with them for a while before connecting the dots.

Common hypothyroidism symptoms

The classic signs reflect a body that's been turned down a notch. You may notice several of these together rather than just one:

• Persistent fatigue and low energy
• Unexplained weight gain
• Feeling cold when others are comfortable (cold intolerance)
• Dry, rough skin
• Hair thinning or hair loss
• Constipation
• Puffy, pale face
• Hoarse voice
• Muscle aches and weakness
• A slowed heart rate
• Low or depressed mood, and trouble with memory
• Changes to your menstrual cycle

How hypothyroidism shows up in your skin, hair, and nails

Because thyroid hormone helps regulate the skin, hair, nails, and sweat glands, the skin is often where an underactive thyroid first becomes visible, which is why a dermatology visit sometimes leads to a thyroid diagnosis.

Dry, scaly skin (xerosis cutis) is the most common skin finding. In a peer-reviewed review of 460 patients, it appeared in 57.16% of people with hypothyroidism. The same review found diffuse hair loss in 46.09%, altered skin texture in 31.74%, and facial swelling (edema) in 28.69%. Skin can feel cool and look pale, and in some cases takes on a yellowish tint from carotene buildup (carotenemia).

Hair and nail changes are common too. Diffuse, partial thinning, sometimes including the outer third of the eyebrows (called madarosis) and even beard or body hair, is described in up to 50% of patients. Nails often become brittle, with increased fragility reported in about 70% of hypothyroid patients, slow growth in 48%, thinning in 40%, and separation of the nail from its bed (onycholysis) in 38%.

In severe, long-standing hypothyroidism, a change called myxedema can develop. Here, water-binding molecules build up in the skin and produce a non-pitting, boggy puffiness, especially around the eyes, hands, and feet.

What causes an underactive thyroid?

In developed countries, the most common cause is Hashimoto's thyroiditis, an autoimmune condition in which the immune system gradually attacks the thyroid. It affects roughly 1 to 2 percent of the population, with most cases appearing between ages 45 and 55, and it's far more common in women. Worldwide, the leading cause is something different: dietary iodine deficiency.

Other causes include thyroid surgery, radiation treatment, certain medications, and, less often, problems with the pituitary gland that signals the thyroid. When the underlying cause isn't specified, clinicians may simply code it as hypothyroidism, unspecified.

How is it diagnosed and treated?

You can't diagnose hypothyroidism from symptoms alone, because so many of them overlap with stress, aging, and other conditions. Diagnosis is confirmed with a simple blood test that measures thyroid-stimulating hormone (TSH) and free T4.

Treatment is usually straightforward. Most people are treated successfully with a once-daily oral medication called levothyroxine, which replaces the hormone the thyroid isn't making. Your clinician adjusts the dose based on follow-up blood tests, and many of the skin, hair, and energy symptoms improve as hormone levels return to normal. Dosing is individualized, so it should always be guided by your own clinician rather than a general guideline.

When to see a doctor

If you're noticing several of these symptoms together, especially fatigue plus dry skin, hair thinning, cold intolerance, or unexplained weight gain that isn't improving, it's worth asking your clinician for a thyroid blood test. This is particularly true for women and for anyone over 60, who are at higher risk.

Most hypothyroidism is mild and far from an emergency, but severe, untreated disease can become serious over time, so don't ignore persistent symptoms. If you ever have profound drowsiness, confusion, or feel intensely cold to the point of seeming unresponsive, that's a medical emergency and you should seek care right away. Otherwise, a routine appointment and a simple blood test are the right next step.