The history of the patient and certain clinical signs seen in the patient can give the treating physician clues regarding the disease. Some of the common findings are:

Poor muscle tone

Sluggish reflexes

Signs of anemia

Visible skin changes - dry coarse rough skin

Goiter - Abnormally enlarged thyroid gland

Basal body temperature

The patient's symptoms and the physician's clinical findings can be confirmed with the following investigations:

Serum T3

Serum T4

Serum TSH

24 hour urine free T3

Antithyroid antibodies (for evidence of autoimmune disease)

Anti-TPO antibodies in the blood (for Hashimoto's thyroiditis)

Thyroid scan

Chest x-ray (may show an enlarged heart)

Serum cholesterol

Testing for anemia (including ferritin)

Prolactin level

If a pituitary or hypothalamic cause is suspected, an MRI of the brain