Elevated TSH – Hypothyroidism

Differential Diagnosis

Hashimoto thyroiditis

Ablative hypothyroidism

Infantile hypothyroidism

Euthyroid sick syndrome

Dangerous Situations

Early diagnosis and treatment of infantile hypothyroidism with thyroid hormone prevents irreversible mental retardation and growth impairment.

Commonly Encountered Situations

Hashimoto thyroiditis accounts for about 90% of all hypothyroidism cases.

Suggested Additional Lab Testing

Hashimoto thyroiditis

• T4 is normal and then becomes low preceding a decline in T3.

• Antithyroid peroxidase and antithyroglobulin tests are positive.

Ablative hypothyroidism: T4 and T3 are low following a procedure that ablates the thyroid gland.

Infantile hypothyroidism: T4 and T3 are low in a newborn or infant.

Euthyroid sick syndrome

• In moderately ill patients, T4 is normal with a low T3, a reverse T3 is elevated, and TSH is normal.

• In severely ill patients, T4 is low with a low T3, an elevated reverse T3, and a low TSH.