That's why the broader symptom pattern matters.

6. Your Bowel Habits Change

Your thyroid can affect the digestive system as well.

An underactive thyroid may slow intestinal movement and contribute to constipation.

Someone who previously had regular bowel movements might begin experiencing:

• Less frequent bowel movements

• Harder stools

• Difficulty passing stool

• A feeling of incomplete evacuation

Hyperthyroidism can have the opposite effect and may contribute to more frequent bowel movements or diarrhea.

Of course, bowel changes are extremely common and can be caused by changes in:

• Fiber intake

• Fluid consumption

• Physical activity

• Medications

• Stress

• Food choices

• Gastrointestinal disorders

A persistent change without an obvious explanation deserves attention.

Particularly important are bowel changes accompanied by blood in the stool, unexplained weight loss, severe abdominal pain, or other concerning symptoms.

7. Your Mood or Mental Focus Changes

Thyroid hormones can influence the nervous system and brain function.

Some people with hypothyroidism report:

• Difficulty concentrating

• Forgetfulness

• Slower thinking

• Low mood

• Reduced motivation

• Feeling mentally “foggy”

Hyperthyroidism can produce a different pattern, including:

• Nervousness

• Irritability

• Restlessness

• Anxiety

• Difficulty concentrating

• Difficulty relaxing

These symptoms can be particularly confusing because they may initially appear psychological rather than physical.

But the relationship goes both ways.