Do thyroid receptors matter? There is often very little if any discussion regarding thyroid receptors. Thyroid receptors are what thyroid hormone (primarily T3) binds to inside your cells. There are also receptors for thyroid hormone on the outside of cells, but that discussion is for another day.
The primary thyroid receptors inside cells are classified as thyroid receptor alpha (TRA) and thyroid receptor beta (TRB).
Today I want to discuss thyroid receptor beta (TRB). Thyroid receptor beta has two forms (called isoforms), TRB1 and TRB2.
Who cares right? Well you should if you are struggling with hypothyroidism and chronic hypothyroid symptoms, especially if you are on thyroid medication and still symptomatic.
TRB2 is found primarily in the central nervous system, hypothalamus, and pituitary gland. TRB1 is found primarily in peripheral tissues.
What very few people seem to understand is that all thyroid receptors do NOT have the same sensitivity to thyroid hormone. Even though thyroid receptor Beta 1 and Beta 2 are very similar, their sensitivity to thyroid hormone is significantly different.
TRB2 is 10X MORE SENSITIVE to T3 than TRB1.
This is likely a protective mechanism. When the brain (CNS), hypothalamus, and pituitary register an influx of T3/4, they can shut down further thyroid production before problems occur of excess thyroid hormone production.
Because the CNS, hypothalamus and pituitary TRB2 receptors are 10x more sensitive, they may become satisfied and shut down thyroid hormone production well before peripheral tissues are satisfied, causing peripheral cellular hypothyroidism.