The first row of a thyroid panel is not a thyroid hormone, and it moves in the opposite direction to the ones that are. That single fact explains most confusion about reading these results.
TSH is a signal, not a product
MedlinePlus: "TSH stands for thyroid stimulating hormone. Another name for it is thyrotropin."
It is made elsewhere: "Your thyroid is controlled by a gland in your brain called the pituitary gland. The pituitary gland makes thyroid-stimulating hormone (TSH)." And its job is instruction — "TSH tells your thyroid how much thyroid hormone it needs to make."
So TSH measures a request, not a result.
Why it runs opposite
Because it is a feedback signal. MedlinePlus describes the loop plainly: "If the thyroid hormone level in your blood is too low, your pituitary gland makes larger amounts of TSH to tell your thyroid to work harder. If your thyroid hormone level is too high, the pituitary gland makes little or no TSH."
Higher demand signal, lower hormone. Lower demand signal, higher hormone. A TSH result read as though it were a thyroid hormone level therefore reads backwards.
Why TSH is usually measured first
MedlinePlus gives the reason: "By measuring the TSH level in your blood, you can find out if your thyroid is making the right level of hormones." Because the pituitary is responding to the hormone levels, the signal carries information about them — which is why many panels start there and only add the hormones themselves when the picture warrants it.
Free vs total
T4 and T3 appear on reports in two forms, and they are different measurements.
Total T4 or T3 counts all of the hormone in the sample, including the large share bound to carrier proteins in the blood.
Free T4 or T3 counts only the unbound fraction.
Because the total includes protein-bound hormone, anything that changes the amount of carrier protein changes the total without the free fraction moving. That is why a panel may report free T4 rather than total T4, and why a free result and a total result for the same hormone are not interchangeable numbers.
Reading the panel
Check which form was measured before comparing across reports — "T4" and "Free T4" are different rows with different reference intervals, and a laboratory switching between them produces a change that looks dramatic and means nothing.
As always, the interval that applies is the one printed on your own report, and MedlinePlus's caution holds: a result outside it "may or may not be a sign of a health problem", and one inside it "isn't always a guarantee of good health."