Zutinic A, Pijl H, Ballieux BE, et al. - In this case-control intervention study, researchers tested the assumption that the thyroid gland of members from long-lived families are less responsive to thyroid stimulating hormone (TSH) stimulation, thereby requiring higher circulating TSH levels to maintain adequate thyroid hormones levels. They conducted a single intramuscular (gluteal) injection with 0.1mg recombinant human TSH in a subgroup of 14 F2-LLS and 15 similarly aged F2-Con. The authors discovered that the AUC fT4/AUC TSH ratio was significantly lower in F2-LLS than in F2-Con. In addition, the AUC Tg/AUC TSH ratio was lower in F2-LLS than in F2-Con. The current findings indicate that members of long-living families have a lower thyroid responsivity to TSH than their partners.