Thyroid analyte levels are interpreted against reference ranges to determine whether concentrations fall within expected limits or demonstrate levels consistent with impaired thyroid hormone production, altered thyroid hormone conversion, or autoimmune-mediated thyroid dysfunction.

• TSH signals the thyroid to produce hormones. Elevated TSH generally suggests reduced thyroid function, whereas suppressed TSH may indicate excessive thyroid hormone activity.

• Free T4 is the primary hormone produced by the thyroid gland and serves largely as a precursor to T3.

• Free T3 is the biologically active thyroid hormone. Low T3 levels indicate reduced availability of the thyroid hormone, which can result in a slowing of metabolic processes.

• Reverse T3 competes with T3 at receptor sites, high levels impair the activity of active T3.

• Ratios assess thyroid hormone conversion efficiency and balance. They help evaluate whether T4 is being effectively converted into active T3 rather than inactive reverse T3.

• TPO Ab are autoantibodies against an enzyme essential for thyroid hormone synthesis. Elevated TPO antibodies are associated with autoimmune thyroid conditions. If identified, treatment for thyroid support changes. 

• ATG Ab are autoantibodies targeting thyroglobulin, a protein involved in thyroid hormone production. Raised levels support autoimmune thyroid dysfunction. If identified, treatment for thyroid support changes. 

• TSH Receptor Ab autoantibodies directed against the TSH receptor can block the receptor, reducing thyroid hormone production and potentially contributing to hypothyroidism.

Blood