If someone with Graves’ disease takes a few doses of a steroid called dexamethasone, their thyroid hormone levels drop quickly—but only for a few days—before going back up again.

When healthy people take a specific dose of a steroid called dexamethasone, it briefly lowers one type of thyroid hormone (T3) but doesn't affect others (T4 or thyroglobulin), which suggests it's changing how the body converts hormones, not how the thyroid gland works.

When people with Graves’ disease take dexamethasone, their thyroid hormone levels drop fast — but that probably isn’t because the medicine is reducing the harmful antibodies, since those don’t disappear that quickly.

Steroid treatment with dexamethasone doesn’t stop the thyroid from responding to hormone signals in people with Graves’ disease — it seems to leave the gland’s inner workings untouched.

In Graves’ disease, there might be something else besides known triggers that’s revving up the thyroid — and dexamethasone could be affecting it, since the hormone changes happen too fast to be just from antibodies.

When someone has Graves’ disease, their thyroid hormones get too high, which tells the brain to stop making a hormone that stimulates the thyroid — so that hormone ends up being very low or even missing in blood tests.