Thyroid Symptoms: When Fatigue Is Something More

Constant fatigue, unexplained weight changes, and feeling too cold or too hot can all be signs of a thyroid problem. The thyroid is a small gland in your neck that sets the pace of your metabolism, and when it runs too slow or too fast, your whole body feels it. Symptoms alone cannot confirm a thyroid condition, but a simple blood test can.

Key Takeaways

• An underactive thyroid (hypothyroidism) tends to slow you down: fatigue, weight gain, feeling cold, dry skin, and low mood, per the NIH.
• An overactive thyroid (hyperthyroidism) speeds you up: weight loss, a racing heart, shakiness, trouble sleeping, and heat intolerance, per the NIH.
• Symptoms overlap with many conditions, so a diagnosis cannot rest on symptoms alone. A blood test is required.
• The first-line check is a TSH blood test, which acts as an early-warning system for how your thyroid is working.
• Routine screening is not recommended for adults with no symptoms, but symptoms or risk factors are a reason to get checked.

What does the thyroid do?

The thyroid makes hormones that control how fast your body uses energy. Think of it as a thermostat for your metabolism. When it makes too little hormone, everything slows down. When it makes too much, everything speeds up. Both patterns are common: nearly 5 in 100 Americans ages 12 and older have an underactive thyroid, and about 1 in 100 have an overactive one.

What are the symptoms of an underactive thyroid?

An underactive thyroid (hypothyroidism) is the "slow" pattern. Symptoms build up gradually and can be easy to miss for months. According to the NIH, common signs include:

• Fatigue and low energy
• Weight gain
• Trouble tolerating cold
• Joint and muscle pain
• Hair loss and dry skin
• Menstrual changes
• Depressed or low mood

The most common cause in the US is Hashimoto's disease, an autoimmune condition that is 4 to 10 times more common in women and often develops between ages 30 and 50.

What are the symptoms of an overactive thyroid?

An overactive thyroid (hyperthyroidism) is the "fast" pattern, and it often looks like the opposite of the list above. Per the NIH, signs include:

• Weight loss despite a normal or bigger appetite
• A rapid or irregular heartbeat
• Nervousness, irritability, or trouble sleeping
• Shaky hands and muscle weakness
• Sweating and heat intolerance
• Fatigue

About 4 out of 5 cases of hyperthyroidism in the US come from Graves' disease, which can also cause eye changes like bulging or light sensitivity in over a third of patients.

How is a thyroid problem tested?

You cannot diagnose a thyroid problem from symptoms, because fatigue, weight change, and mood shifts have so many causes. The first step is a TSH (thyroid-stimulating hormone) blood test. TSH comes from the pituitary gland and tells the thyroid to work. When the thyroid underproduces, TSH rises; when it overproduces, TSH falls. That makes it a sensitive early-warning check. If your TSH is off, your clinician may add a Free T4 test, and sometimes thyroid antibodies, to see the full picture.

For most adults, a normal TSH sits roughly between 0.4 and 4.0 mIU/L, but this is approximate. Every lab prints its own reference range, and pregnancy uses different targets, so always read your result against the range on your own report. If you want help making sense of a lab report, our guide on understanding your blood test results walks through it.

When should I get my thyroid checked?

For adults with no symptoms, the USPSTF found there is not enough evidence to recommend routine screening. That guidance does not apply if you have symptoms or risk factors. Talk with a clinician about a thyroid test if you have:

• Persistent fatigue paired with weight change, cold or heat intolerance, or mood changes
• A lump or swelling in your neck (a goiter)
• A family history of thyroid or autoimmune disease, a recent pregnancy, or past thyroid treatment

Some symptoms need prompt attention. Bulging eyes, double vision, or eye pain deserve a quick medical evaluation. If you take antithyroid medication, seek care right away for fever, a persistent sore throat, mouth sores, yellowing of the skin or eyes, or severe fatigue, since these can signal serious side effects. A very rapid or irregular heartbeat with high fever and confusion is a medical emergency; call 911.

Your care team at Morningside Medical adult primary care can order a TSH test, explain the result in plain language, and build a plan that fits you. Feeling tired all the time is not something you have to just live with. If your body feels off, it is worth a conversation.

This article is for general information and is not a substitute for professional medical advice. Talk to your clinician about your specific situation.

Book an appointment with our team and let us help you find out what is behind how you feel.