Patients with goiter may be in a euthyroid, hypothyroid or hyperthyroid state. Patients should be evaluated for free tetraiodothyronine (T4), Triiodothyronine (T3), thyroid stimulating hormone (TSH) levels and thyroid peroxidase (TPO) antibodies.

Thyroid function tests:

• Patients with goiter may be in a euthyroid, hypothyroid or hyperthyroid state.
• When the serum TSH is below normal levels, then the serum free T4 and T3 should be evaluated. The most likely diagnosis in patients with overt or subclinical hyperthyroidism and goiter, may be either multinodular goiter (MNG) or Grave’s disease.
• When the TSH is above normal levels, then the free T4 should be evaluated. Hashimoto’s thyroiditis is the most probable diagnosis in patients presenting with overt or subclinical hypothyroidism, except for patients living in areas of iodine deficiency leading to endemic goiter.

Thyroid peroxidase antibodies (TPO): ^[1]

• In patients with goiter, serum TPO antibodies have to be evaluated. In patients with goiter and and normal TSH levels, TPO antibodies are measured to rule out Hashimoto’s thyroiditis.
• In the United States, TPO antibodies are mostly elevated in patients with elevated TSH (hypothyroidism) and goiter, and the most likely diagnosis is Hashimoto’s thyroiditis.

The following laboratory testing should be carried out if a patient presents with goiter:

• Serum TSH
• Serum T3
• Serum T4
• Serum thyroglobulin
• Serum cholesterol
• Thyroid scintigraphy

• Anti-TPO antibodies detected in most autoimmune thyroid disease (eg, Hashimoto’s thyroiditis, idiopathic Myxedema, and Grave’s disease)
• Urinary iodine level less than 10 mcg/dL is suggestive of iodine deficiency