TSH receptor

The TSH receptor is the thyroid’s on-switch and accelerator pedal in one. It is the antenna on follicular cells that listens for the pituitary’s order to make hormone, and how hard it is pressed sets how much the gland produces and how big it grows.

Sitting in the membrane of the follicular cell, it is a G protein-coupled receptor: when thyroid-stimulating hormone binds, it raises cyclic AMP inside the cell, ramping up iodide trapping, hormone synthesis, and release, and over time stimulating the cells to divide. This single receptor therefore links the whole hypothalamic-pituitary-thyroid axis to actual hormone output.

Because the switch can be flipped abnormally, it sits at the center of two important diseases. In Graves’ disease, antibodies bind and constantly activate the receptor, driving relentless hyperthyroidism independent of pituitary control. Conversely, blocking antibodies or inactivating mutations can leave the gland unresponsive, causing hypothyroidism. Measuring TSH-receptor antibodies is a standard test when Graves’ disease is suspected.