Hyperthyroidism

Laboratory tests in 6 weeks

• TSH
• Free T4 as a reflex test if TSH remains lowif neededTSH confirmed low (between 0.1 and 0.4 mIU/L) on repeat: free T4 as a reflex test on the same sample, then free T3 as a reflex test if free T4 is normal ^[1].
• State on the request: "follow-up TSH, reflex assays".

Laboratory tests

• TSH
• Free T4
• TSH receptor antibodies (TRAb)
• free T3 assay if TSH low and free T4 normalif neededIf TSH low and free T4 normal.
• CRPif neededSuspected De Quervain thyroiditis (raised CRP).
• Thyroglobulin (if factitious thyrotoxicosis suspected)if neededSuspected covert intake of thyroid hormones: a low or undetectable thyroglobulin, in the absence of anti-thyroglobulin antibodies, establishes the diagnosis ^[1].
• Anti-thyroglobulin antibodies (with thyroglobulin, if factitious thyrotoxicosis suspected)if neededSuspected covert intake of thyroid hormones: anti-thyroglobulin antibodies validate the thyroglobulin measurement ^[1,2].

Laboratory tests before starting treatment

• FBC
• TSH
• Free T4 (or free T3 in T3 hyperthyroidism)
• ASTWarning sign of hepatitis; the SFE and the GRT also suggest a check before initiation and after 3 or 4 weeks.
• ALTWarning sign of hepatitis; the SFE and the GRT also suggest a check before initiation and after 3 or 4 weeks.
• GGTWarning sign of hepatitis; the SFE and the GRT also suggest a check before initiation and after 3 or 4 weeks.
• Alkaline phosphataseWarning sign of hepatitis; the SFE and the GRT also suggest a check before initiation and after 3 or 4 weeks.

FBC every week for the first 6 weeks

• FBC (one a week, 6 in total)
• If fever, sore throat or sign of infection: stop the antithyroid drug and do an urgent FBC.

Laboratory tests between day 21 and day 42

• Free T4 (or free T3 in T3 hyperthyroidism)
• Free T3 (in addition to free T4)if needednon-French guidelineAmerican and British practice: the American Thyroid Association measures free T4 and T3 from 2 to 6 weeks of treatment, as free T4 may normalise while T3 remains high ^[4]; NICE measures TSH, free T4 and free T3 every 6 weeks until TSH normalises ^[3]. HAS asks for free T3 only if it was initially abnormal ^[1].
• ASTif neededWarning sign of liver damage (jaundice, pale stools, dark urine, abdominal pain, pruritus): liver function tests without delay ^[1,8]. No consensus for routine monitoring ^[1,9]; stop the antithyroid drug if clinical hepatitis or transaminases > 3 times normal ^[9].
• ALTif neededWarning sign of liver damage (jaundice, pale stools, dark urine, abdominal pain, pruritus): liver function tests without delay ^[1,8]. No consensus for routine monitoring ^[1,9]; stop the antithyroid drug if clinical hepatitis or transaminases > 3 times normal ^[9].
• GGTif neededWarning sign of liver damage (jaundice, pale stools, dark urine, abdominal pain, pruritus): liver function tests without delay ^[1,8]. No consensus for routine monitoring ^[1,9]; stop the antithyroid drug if clinical hepatitis or transaminases > 3 times normal ^[9].
• Alkaline phosphataseif neededWarning sign of liver damage (jaundice, pale stools, dark urine, abdominal pain, pruritus): liver function tests without delay ^[1,8]. No consensus for routine monitoring ^[1,9]; stop the antithyroid drug if clinical hepatitis or transaminases > 3 times normal ^[9].

Laboratory tests at day 60 (M2)

• Free T4 (or free T3 in T3 hyperthyroidism)
• Repeat every 3-6 weeks until free T4 normalises

TSH every 2 to 4 months thereafter

• TSH

Before the decision to stop treatment

• TSH receptor antibodies

After stopping: at 6-8 weeks, 3 months, 6 months and 12 months

• TSH (6 to 8 weeks, 3, 6 and 12 months after stopping, then at least once a year)
• Free T4 as a reflex test if TSH is lowif neededLow TSH at a check: free T4 is measured as a reflex test on the same sample ^[1,2].
• Free T3 as a reflex test (initial T3 hyperthyroidism)if neededT3 hyperthyroidism: low TSH and normal free T4, free T3 is measured as a reflex test ^[1].

Laboratory tests

• TSH
• Free T4
• Free T3
• TSH receptor antibodies (TRAb)
• Anti-thyroid peroxidase (TPO) antibodies
• FBC (neutrophils)if needednon-French guidelineConfirmed hyperthyroidism: baseline tests before an antithyroid drug, as both the disease and the treatment can alter neutrophils and liver function tests ^[15].
• ASTif needednon-French guidelineConfirmed hyperthyroidism: baseline tests before an antithyroid drug, as both the disease and the treatment can alter neutrophils and liver function tests ^[15].
• ALTif needednon-French guidelineConfirmed hyperthyroidism: baseline tests before an antithyroid drug, as both the disease and the treatment can alter neutrophils and liver function tests ^[15].