• Free T4

• Sometimes free T3

• Thyroid antibody tests

• Additional testing based on symptoms and medical history

These tests help determine whether the thyroid is producing too little or too much hormone and, in some cases, help identify the underlying cause.

A physical examination may also include checking the neck for thyroid enlargement or nodules.

In some situations, imaging such as a thyroid ultrasound may be recommended.

Hypothyroidism vs. Hyperthyroidism

It can help to understand the basic difference.

Hypothyroidism

The thyroid doesn't produce enough thyroid hormone.

Possible symptoms include:

• Fatigue

• Weight gain

• Cold intolerance

• Constipation

• Dry skin

• Hair changes

• Slower heart rate

• Muscle aches

• Depression or low mood

• Difficulty concentrating

Hyperthyroidism

The thyroid produces too much thyroid hormone.

Possible symptoms include:

• Weight loss

• Heat intolerance

• Excessive sweating

• Rapid heartbeat

• Anxiety

• Trembling

• Increased bowel movements

• Difficulty sleeping

• Muscle weakness

• Increased appetite

Not everyone experiences the same symptoms, and some people have relatively few noticeable symptoms.

What Causes Thyroid Problems?

There are several possible causes.

One of the most common causes of hypothyroidism is Hashimoto's thyroiditis, an autoimmune condition in which the immune system attacks thyroid tissue.