What are the common symptoms of thyroid dysfunction?

Underactive thyroid

Persistent fatigue that rest does not fix, unexplained weight gain or difficulty losing weight, feeling cold when others are comfortable, constipation, dry skin and brittle nails, hair thinning including the outer eyebrows, puffiness around the face and eyes, low mood, and a general sense of mental slowness.

Muscle aches, joint stiffness, and a hoarse voice also appear commonly and are frequently overlooked as thyroid-related.

Overactive thyroid

Weight loss despite a normal or increased appetite, feeling hot and sweating more than usual, a racing or irregular heartbeat, palpitations, anxiety and restlessness, hand tremor, frequent bowel movements, muscle weakness, and difficulty falling or staying asleep.

Eye changes — irritation, bulging, or double vision — can occur with Graves’ disease specifically and warrant prompt assessment.

Why these are so often missed

The symptoms are non-specific and overlap heavily with depression, perimenopause, iron deficiency, sleep disorders, and simply being busy and under-slept. They usually develop slowly enough that people adjust to them without noticing.

That overlap is exactly why symptoms should prompt testing rather than a conclusion — and why a full panel is more informative than TSH alone when symptoms persist despite a normal screening result.