Department of Endocrinology, Oxford University Hospitals NHS Trust, OCDEM, Oxford OX3 7LJ, UK.
Eur J Endocrinol. 2013 May 10;168(6):913-7. doi: 10.1530/EJE-12-1035. Print 2013 Jun.
For patients who remain hypothyroid despite the administration of what would seem adequate doses of levothyroxine (L-T4), the underlying cause can be difficult to determine. The possibility of a biological cause should first be explored; however, in the majority of cases, poor adherence to medication is likely to be the main cause of treatment failure. When non-adherence is suspected but not volunteered, options to confirm the suspicion are limited. In this study, we identified patients for whom known drugs and pathological causes of L-T4 malabsorption were excluded, and despite often high doses of L-T4, the patients remained hypothyroid.
Using a weight-determined oral L-T4 bolus administration, absorption was initially assessed in 23 patients. In nearly all patients, this was shown to be maximal at 120 min post-ingestion. This was then followed by the continued administration of a weekly T4 bolus for a 4-week period after which TSH and free T4 (fT4) levels were recorded.
All patients showed a rise in fT4 at 120 min following the administration of the L-T4 bolus, with a mean increase of 54±3% from baseline. Following the treatment period, using an equivalent weekly L-T4 dose, which was significantly less than that of the daily dose taken by the patients before the test, TSH reduced from baseline in ~75% of cases.
Using this combination of tests allows significant malabsorptive problems to be identified first and then potential non-adherence to be demonstrated. A management plan can then be implemented to increase adherence, aiming to improve treatment outcomes.
对于尽管给予了看似足够剂量的左甲状腺素（L-T4）仍持续甲状腺功能减退的患者，其根本原因可能难以确定。首先应探讨是否存在生物学原因；但是，在大多数情况下，极有可能是药物治疗依从性差导致治疗失败。当怀疑但未主动报告不依从时，确认怀疑的选择有限。在这项研究中，我们确定了已知药物和 L-T4 吸收不良的病理原因已排除的患者，尽管他们经常服用高剂量的 L-T4，但仍存在甲状腺功能减退。
使用基于体重的口服 L-T4 冲击式给药，最初在 23 名患者中评估了吸收情况。几乎所有患者在摄入后 120 分钟时均显示出最大吸收。然后，在接下来的 4 周内每周继续给予 T4 冲击式给药，之后记录 TSH 和游离 T4（fT4）水平。
所有患者在给予 L-T4 冲击式给药后 120 分钟时 fT4 升高，与基线相比平均增加 54±3%。在治疗期间，使用等效的每周 L-T4 剂量，该剂量明显低于患者在测试前每天服用的剂量，约 75%的患者 TSH 从基线下降。
使用这些测试组合可以首先发现明显的吸收不良问题，然后再证明潜在的不依从性。然后可以实施管理计划来提高依从性，旨在改善治疗结果。
