Comparison of thyroid function test abnormalities in syndromes of impaired sensitivity to thyroid hormone

TSH: thyroid-stimulating hormone; THCMTD: thyroid hormone cell membrane transport defect; THMD: thyroid hormone metabolism defect; RTH-beta: TR-beta gene defects; TR-beta: thyroid hormone receptor beta; ADD: attention deficit disorder; RTH-alpha: TR-alpha gene defects; TR-alpha: thyroid hormone receptor alpha; RTH: resistance to thyroid hormone; TR: thyroid hormone receptor; sl: slight; N: normal; ↑: increased; ↓: decreased.
* The term "resistance to thyroid hormone" (RTH) traditionally described a clinical and biochemical phenotype. Now, this phenotype is divided into the mechanistic categories of RTH-beta and non-thyroid hormone receptor RTH (nonTR-RTH), which are distinguished by the presence or absence of a mutation in the TR-beta gene.
¶ The mechanism for nonTR-RTH is unknown but probably involves abnormal cofactors or substances that interfere with the action of thyroid hormone on its receptor.