SLC16A2 and Global developmental delay: The TH profile of all female index patients clearly differed from asymptomatic carriers and noncarriers with the total T3/total rT3 and total T3/free T4 ratios being elevated, confirming previous findings suggesting that elevated free T3/free T4 ratios can be used in (female) patients with developmental delay to indicate MCT8 deficiency or other TH resistance syndromes (30).