How do you read a thyroid report?

TSH is the main screening test and behaves inversely — high TSH generally indicates an underactive thyroid, low TSH an overactive one. Free T4 is added to confirm and grade. Subclinical hypothyroidism, where TSH is mildly raised but T4 is normal, is common and whether it needs treating depends on the degree, symptoms, antibody status and whether you are pregnant or trying to conceive. Thyroid antibodies indicate an autoimmune cause, which predicts progression. Timing matters: take the sample in the morning and, if you are on treatment, before that day's dose.