Do Nhan Van, Mino Lizbeth, Merriam George R, LeMar Homer, Case H Samuel, Palinkas Lawrence A, Reedy Kathleen, Reed H Lester
Internal Medicine Service, Madigan Army Medical Center, Tacoma, Washington 98431, USA.
J Clin Endocrinol Metab. 2004 Apr;89(4):1529-33. doi: 10.1210/jc.2003-031747.
Extended Antarctic residence (AR) is associated with an increase in serum TSH, a decrease in free T(4), and an increase in T(3) production and clearance. It is not clear whether these adaptations reflect changes in clearance alone or whether intrinsic thyroidal synthetic activity also changes. Thyroglobulin (Tg) secretion is an independent marker of intrinsic thyroid activity whose kinetics are independent of those of T(3) and T(4). In this study we examined changes in Tg levels in healthy subjects before and during AR and their responses to thyroid supplementation to help determine whether alterations in thyroid activity, and not just kinetics of clearance, underlie the changes seen with the polar T(3) syndrome. In cohort 1, we compared measurements of TSH and Tg in 12 subjects before deployment and monthly for 11 months during AR. In cohort 2, we compared the same measurements in 12 subjects monthly for 11 months of AR. Subjects were randomized to receive either placebo or levothyroxine in cohort 1 for 7 months and in cohort 2 for 11 months. Tg increased over baseline during the first 4 months of AR by 17.0 +/- 4.6% and after 7 more months by 31.7 +/- 4.3% over baseline in the placebo group of both cohorts (P < 0.0002). When L-T(4) was taken, Tg returned to a value not different from baseline (4.5 +/- 3.9%). The percent changes from baseline in serum TSH and Tg during AR were highly correlated (P < 0.00003) in the placebo group for both cohorts. The rise in Tg with TSH and the reduction in Tg with L-T(4) provide evidence of target tissue response to TSH and further confirm the TSH rise as physiologically significant. The results also suggest that the adaptive changes in thyroid hormone economy with AR reflect TSH-dependent changes in thyroid synthetic activity, which may help explain a portion of the increases in T(3) production found with AR.
长期南极居住（AR）与血清促甲状腺激素（TSH）升高、游离甲状腺素（T4）降低以及T3生成和清除增加有关。目前尚不清楚这些适应性变化是仅反映清除率的改变，还是甲状腺内在合成活性也发生了变化。甲状腺球蛋白（Tg）分泌是甲状腺内在活性的一个独立标志物，其动力学与T3和T4的动力学无关。在本研究中，我们检测了健康受试者在AR之前和期间Tg水平的变化以及他们对甲状腺补充剂的反应，以帮助确定甲状腺活性的改变，而不仅仅是清除动力学的改变，是否是极地T3综合征所见变化的基础。在队列1中，我们比较了12名受试者在部署前以及AR期间11个月每月一次的TSH和Tg测量值。在队列2中，我们比较了12名受试者在AR的11个月中每月一次的相同测量值。在队列1中，受试者被随机分配接受安慰剂或左甲状腺素7个月，在队列2中接受11个月。在两个队列的安慰剂组中，AR的前4个月Tg比基线升高了17.0±4.6%，再过7个月后比基线升高了31.7±4.3%（P<0.0002）。服用L-T4时，Tg恢复到与基线无差异的值（4.5±3.9%）。在两个队列的安慰剂组中，AR期间血清TSH和Tg相对于基线的百分比变化高度相关（P<0.00003）。Tg随TSH升高以及随L-T4降低提供了靶组织对TSH反应的证据，并进一步证实TSH升高具有生理意义。结果还表明，AR导致的甲状腺激素代谢适应性变化反映了甲状腺合成活性中TSH依赖性变化，这可能有助于解释AR时发现的T3生成增加的一部分原因。
