Treatment: antithyroid drugs

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 guidelineUS and UK practice: the American Thyroid Association measures free T4 and T3 from 2 to 6 weeks of treatment, because free T4 may normalise while T3 remains high ^[2]; 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 ^[4].
• ASTif neededWarning sign of liver injury (jaundice, pale stools, dark urine, abdominal pain, pruritus): liver function tests without waiting ^[4,5]. No consensus on routine monitoring ^[4,6]; clinical hepatitis or transaminases > 3 times normal require stopping the antithyroid drug ^[6].
• ALTif neededWarning sign of liver injury (jaundice, pale stools, dark urine, abdominal pain, pruritus): liver function tests without waiting ^[4,5]. No consensus on routine monitoring ^[4,6]; clinical hepatitis or transaminases > 3 times normal require stopping the antithyroid drug ^[6].
• GGTif neededWarning sign of liver injury (jaundice, pale stools, dark urine, abdominal pain, pruritus): liver function tests without waiting ^[4,5]. No consensus on routine monitoring ^[4,6]; clinical hepatitis or transaminases > 3 times normal require stopping the antithyroid drug ^[6].
• Alkaline phosphataseif neededWarning sign of liver injury (jaundice, pale stools, dark urine, abdominal pain, pruritus): liver function tests without waiting ^[4,5]. No consensus on routine monitoring ^[4,6]; clinical hepatitis or transaminases > 3 times normal require stopping the antithyroid drug ^[6].

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 (after 12 to 18 months of treatment)

• TSH receptor antibodies (TRAb)
• TSH

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

• TSH (at each date)
• 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 ^[4,13].