Bloods

• Thyroid function - TSH, free T4 and Total T3, (or free T3, depending on lab).
• Initially performed to confirm Thyrotoxicosis.
• Expect suppressed TSH and either or both of raised fT4 or Total T3 (some children with thyrotoxicosis have raised T3 but normal T4).
• Antibodies – To confirm Autoimmune thyrotoxicosis and distinguish Graves’ from Hashimotos.
• TSH receptor antibodies(TRAb) – Presence suggests Graves’ Disease.
• Thyroid Peroxidase antibodies(TPO) - can be present in both Graves’ and Hashimoto’s disease.
• Children with persistently high levels of TSH receptor antibodies after treatment with antithyroid medications are more likely to relapse when treatment is discontinued.

Secondary investigations (if available or if diagnosis in doubt)

• Ultrasound of thyroid – diffusely enlarged thyroid in Graves, focal enlargement in nodule.
• Assessment of thyroid volume by ultrasound.
• Technitium (Tc 99m) or iodine (123 I) uptake scan – diffusely enlarged in Graves, focal uptake in nodule, diminished uptake in thyroiditis.

Other Investigations of possible or research merit

• Bone age – may be advanced.
• DEXA – reduced bone density.