The history and physical examination generally reveal the characteristic
symptoms and physical signs that suggest hypothyroidism; however, laboratory
evaluation is necessary to establish the diagnosis and cause of
Diagnostic lab tests include measuring the blood levels of:
- Thyroid stimulating hormone (TSH). This hormone will
be elevated in cases of hypothyroidism. The TSH assay is the most sensitive test
for the diagnosis of hypothyroidism.
- Free T4 (free thyroxine) and T3 thyroid hormones.
Thyroid hormone levels in the blood will be low, but with mild, or "subclinical"
hypothyroidism, the thyroid hormone levels can be in the low normal range.
- Thyroid autoantibodies (anti-thyroid peroxidase and antithyroglobulin autoantibodies). The presence of these antibodies indicates autoimmune thyroiditis (Hashimoto's
disease) as the underlying cause of
Stephanie L Lee, MD, PhD, FACE
Sonia Ananthakrishnan, MD
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