Figure 7.
Role of D2 and D3 in thyroid hormone signaling. T4 and T3 are represented by blue and green circles, whereas D2 and D3 homodimers are represented by brown and yellow ovals. A, D3 catalyzes the conversion of plasma and cellular T4 and T3 to the inactive metabolites rT3 and T2, respectively, decreasing the nuclear pool of T3 available to occupy TRs. B, In D2-expressing cells, the nuclear pool of T3 available to the TRs originates from both plasma T3 and T3 generated via D2. [Modified with permission from Bianco et al.: Endocrinology 148:3077–3079, 2007 (445). ©The Endocrine Society.]