Verify member benefits — policy statements do not guarantee authorization

Coverage and payment are determined by the member's benefit plan at the time of the request; the medical policy statement does not guarantee authorization or payment. Verify plan contract/Evidence of Coverage and applicable government policies before ordering or submitting claims.

No explicit prior‑auth rules; follow guideline‑directed selective testing

The policy does not specify a formal prior authorization program for thyroid testing; however, testing should be targeted (not universal) per guideline recommendations and first-line testing guidance (TSH first-line when indicated).

Avoid routine ultrasound or routine T3 testing — require justification

Routine thyroid ultrasound without palpable abnormalities and routine T3 testing for LT4 dosing are discouraged; imaging or additional tests require clinical justification tied to palpable findings or specific indications.

Procedure codes listed as reference — verify billing/payment

Procedure/CPT codes listed in the policy are for reference only and do not guarantee payment; providers should verify billing and authorization expectations with the payer and local coverage determinations before ordering.

Newly referenced CPT code (83520) — note addition

CPT code 83520 was added in the revision history and is now referenced in the policy; treat this code as newly included in the policy's code list for billing/reference purposes.

• 83520 appears in the policy's CPT list and revision notes.

No step‑therapy specified; follow laboratory‑first testing sequence

This policy section does not specify step therapy for medications; laboratory sequencing guidance (TSH first-line; prefer fT4 over total T4 except in pregnancy) describes testing order rather than drug-step requirements.

Order TSH first; prefer fT4 (use total T4 methods in pregnancy when needed)

Use serum TSH as the first‑line test when testing is indicated; measure fT4 rather than total T4 to diagnose hypothyroidism except in pregnancy where total T4 or trimester‑specific methods are acceptable.

• ASCP and guideline recommendations: start with TSH and confirm with fT4 as indicated.

Follow recommended test sequencing and serial monitoring algorithms

Follow guideline sequencing and serial monitoring: repeat testing per scenario (e.g., measure TSH then reflex fT4/FT3 per NICE cascade; in CeH monitor FT4 as indicated). Order follow‑up tests only as recommended by the diagnostic algorithm.

• NICE cascade: measure TSH first when secondary dysfunction not suspected, then add FT4/FT3 per result.
• ETA/CeH guidance: monitor FT4 and TSH biannually in childhood, yearly later.

Observe monitoring intervals — 6‑week minimum after dose change; annual when stable

Adhere to specified monitoring intervals when managing treated thyroid disease: for primary hypothyroidism recheck no more frequently than 6 weeks after dose changes and annually when stable; for secondary (central) hypothyroidism monitor fT4 every 6 weeks after dose change and annually when stable.

• Hypothyroidism: no more frequently than 6 weeks after dose change; annual once stable.
• Secondary hypothyroidism: fT4 every 6 weeks after dose change; annual once stable.

Document clinical indication, symptoms, pregnancy status, and medication exposure

Document clinical signs/symptoms consistent with thyroid dysfunction, pregnancy/postpartum status, medication exposures affecting thyroid function, and history of thyroid disease or neoplasm to support medical necessity for testing.

• Include documentation of symptoms listed in policy Note 1/Note 2 when applicable.
• Record medication exposures and timing relative to testing.

Document pregnancy‑specific risk factors to justify targeted testing

In pregnancy, document risk factors that justify targeted thyroid testing (history of thyroid dysfunction or surgery; TPOAb positivity; age >30; type 1 diabetes or other autoimmune disease; prior miscarriage or preterm delivery; goiter; use of amiodarone or lithium; infertility; recent iodinated contrast exposure; morbid obesity; residence in iodine‑deficient area).

• Apply trimester‑ and assay‑specific reference ranges when documenting pregnancy testing.

When ordering frequent testing, document trimester, prior thyroid history and exposures

When ordering frequent or trimester‑specific testing, document clinical context including pregnancy trimester, prior thyroid history (ablation, surgery), exposures (eg, alemtuzumab), and other risk factors that justify short‑interval monitoring.

• For IRT (e.g., alemtuzumab) document therapy timing; ETA recommends TSH every 3 months post‑IRT.
• For pregnancy document trimester and reason for 4‑week monitoring.

Require paired FT4 + TSH confirmation for central hypothyroidism (≥2 determinations)

Confirm suspected central hypothyroidism (CeH) with combined laboratory evidence: FT4 below the laboratory lower limit with inappropriately low/normal TSH on at least two separate determinations, measured together and after exclusion of listed causes.

• ETA: require FT4 low and TSH low/normal on >=2 determinations; consider >20% FT4 drop as supportive when using same assay.

Record indication and intended timing/interval when ordering repeat thyroid tests

When ordering TSH and fT4/fT3 for monitoring or diagnostic scenarios, document the clinical indication and the planned timing/interval for repeat testing per the applicable clinical scenario (e.g., pregnancy, dose change, CeH follow‑up).

• Record intended monitoring interval (eg, 4 weeks in pregnancy during adjustment; 6 weeks after hypothyroid dose change).

Denial risk: TRH, TBG, reverse T3, T3 uptake, total T4, TT3/fT3 in many contexts

Requests for TRH or TBG testing, reverse T3, T3 uptake, and total T4 in contexts not specified by the policy, as well as TT3/fT3 to assess LT4 dosing, do not meet coverage criteria and are at risk for denial.

• TBG is explicitly listed as not covered under any circumstances.
• Measurement of TT3/fT3 for levothyroxine dosing does not meet coverage.

Monitoring gap risk — ensure regular TSH monitoring on therapy

Failure to monitor TSH regularly in patients on thyroid medication may represent underuse and could lead to gaps in care; ensure TSH monitoring at recommended intervals (eg, as outlined for dose changes and stabilization).

• Study cited: 40% of patients with thyroid disorders did not receive a monitoring TSH within one year.

Excess initial testing risk — start with TSH then confirm with fT4

Avoid ordering extensive initial thyroid panels without starting with TSH and confirmatory fT4; broad initial panels may be inconsistent with ASCP guidance and could prompt medical‑necessity review.

• ASCP recommends starting with TSH and confirming diagnosis with fT4 rather than ordering multiple tests up front.

Government/local coverage supersedes this policy when conflicts exist

If a federal or state government coverage policy (NCD/LCD or Medicaid) conflicts with this policy for a specific member, the government policy governs and may change adjudication or lead to denial if inconsistent with this policy.

Non‑covered tests: TRH and TBG are excluded — high denial risk

Testing for TRH or TBG does not meet coverage criteria and is explicitly excluded; billing for these tests when used to evaluate cause of hyper‑ or hypothyroidism is a denial risk.