Thyroid problems are extremely common. Some estimates suggest millions of cases go undiagnosed, often because symptoms develop gradually and lab tests do not always tell the whole story.

The thyroid gland is a small, butterfly-shaped gland at the base of the neck. It acts as the body’s metabolic thermostat, regulating how quickly the body uses energy.

When the thyroid is not functioning properly, many systems in the body can be affected. Diagnosis is not always straightforward. Lab tests are helpful, but symptoms and body temperature patterns can also provide important clues.

Common Thyroid Lab Tests

TSH

TSH (thyroid-stimulating hormone) is produced by the pituitary gland and signals the thyroid to produce hormone. For reasons that are not entirely clear, many doctors rely heavily on this test to diagnose hypothyroidism. However, TSH is not a thyroid hormone, and relying on it alone may miss some cases of thyroid dysfunction.

Click here to learn more about TSH testing.

T4 (Thyroxine)

T4 is the primary hormone produced by the thyroid gland. It is relatively inactive and must be converted into T3, the active thyroid hormone.

T3

T3 is the active thyroid hormone that affects metabolism in the body’s tissues. It is produced when one iodine atom is removed from T4.

Reverse T3 (RT3)

Reverse T3 is an inactive form of thyroid hormone. Elevated reverse T3 may interfere with thyroid hormone activity and can sometimes make thyroid tests appear normal even when symptoms are present.

Thyroid Autoantibody Tests

Autoantibody tests help detect autoimmune thyroid disease.

Common tests include:

  • Thyroid Peroxidase Antibodies (TPOAb)

  • Thyroglobulin Antibodies (TgAb)
    (often seen in Hashimoto’s thyroiditis)

  • Thyroid-Stimulating Immunoglobulin (TSI)

  • Thyrotropin Receptor Antibodies (TRAb)
    (associated with Graves’ disease)

Symptoms

Hypothyroidism (Low Thyroid)

Common symptoms include:

  • fatigue

  • depression or low mood

  • lack of motivation

  • dry skin

  • constipation

  • cold intolerance

  • weight gain or difficulty losing weight

Untreated hypothyroidism may contribute to:

Hyperthyroidism (Overactive Thyroid)

Hyperthyroidism can sometimes become a medical emergency if severe.

Symptoms may include:

  • unexplained weight loss

  • rapid or irregular heartbeat

  • nervousness or anxiety

  • heat intolerance

  • trembling hands

  • excessive sweating

  • insomnia

  • frequent bowel movements

In Graves’ disease, eye symptoms such as irritation or bulging eyes may occur.

Autoimmune Thyroid Disease

Two common autoimmune thyroid disorders are:

Hashimoto’s Thyroiditis

The immune system attacks the thyroid gland, often leading to hypothyroidism over time.

Graves’ Disease

The immune system overstimulates the thyroid gland, leading to hyperthyroidism.