Levothyroxine absorption test in patients with refractory hypothyroidism: how to interpret patient's response to the test?

IF 3 3区医学 Q2 ENDOCRINOLOGY & METABOLISM

Endocrine Pub Date : 2025-06-14 DOI:10.1007/s12020-025-04312-w

Ibtissem Oueslati, Ameni Terzi, Meriem Yazidi, Elyes Kamoun, Moncef Feki, Melika Chihaoui

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引用次数: 0

Abstract

Introduction: Levothyroxine (LT4) absorption test is indicated in patients with refractory hypothyroidism to distinguish between pseudo-malabsorption and malabsorption. However, this test is not standardized and its interpretation remains controversial. The aim of the present study was to evaluate the different interpretations of the LT4 absorption test to confirm or infirm a disorder of LT4 absorption in patients with refractory hypothyroidism.

Methods: This was a retrospective study including patients who were admitted for refractory hypothyroidism. LT4 absorption test was performed in all patients. Four different equations were used to interpret the test: The LT4 absorption rate, FT4 increment, FT4 increase rate, and FT4 ratio. Celiac disease serology and digestive endoscopy with biopsy were performed in all patients.

Results: Seven patients were enrolled in this study. Their median age was 38 years. The median duration of hypothyroidism was 2.6 years. The median dose of LT4 was 4 µg/kg/day. Before the LT4 absorption test, the median TSH and FT4 levels were 72.59 mIU/L and 0.52 ng/dL, respectively. Using LT4 absorption rate and FT4 ratio formulas, the test was consistent with the diagnosis of malabsorption in all patients. However, when using FT4 increase rate, four patients (P1, P2, P4, and P5) had malabsorption and three patients (P3, P6, and P7) had pseudo-malabsorption. According to the FT4 increment, six patients (P1, P2, P4, P5, P6, and P7) had malabsorption and one patient (P3) had pseudo-malabsorption. Etiological investigations revealed the presence of Helicobacter pylori gastritis in four patients (P1, P2, P4, and P5). Patients 3, 6, and 7 admitted non-compliance with LT4 treatment when confronted with evidence about pseudo-malabsorption.

Conclusion: The FT4 increase rate seemed more effective than LT4 absorption rate, FT4 ratio, and FT4 increment in differentiating pseudo-malabsorption from malabsorption. However, further multicenter studies involving larger sample sizes would be useful to confirm these findings.

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难治性甲状腺功能减退患者的左甲状腺素吸收试验：如何解释患者对该试验的反应？

简介：左旋甲状腺素（LT4）吸收试验适用于难治性甲状腺功能减退患者，以区分假吸收不良和吸收不良。然而，这项测试没有标准化，其解释仍然存在争议。本研究的目的是评估LT4吸收试验的不同解释，以确认或削弱难治性甲状腺功能减退患者LT4吸收障碍。方法：这是一项回顾性研究，包括顽固性甲状腺功能减退患者。所有患者均行LT4吸收试验。采用4个不同的方程来解释试验：LT4吸收率、FT4增量、FT4增幅和FT4比率。所有患者均进行了乳糜泻血清学检查和消化内镜活检。结果：7例患者入组。他们的平均年龄为38岁。甲状腺功能减退的中位病程为2.6年。LT4的中位剂量为4µg/kg/天。在LT4吸收试验前，TSH和FT4水平中位数分别为72.59 mIU/L和0.52 ng/dL。使用LT4吸收率和FT4比值公式，试验结果与所有患者的吸收不良诊断一致。然而，当使用FT4增加率时，4例患者（P1、P2、P4、P5）出现吸收不良，3例患者（P3、P6、P7）出现假吸收不良。根据FT4增量，6例患者（P1、P2、P4、P5、P6、P7）存在吸收不良，1例患者（P3）存在假性吸收不良。病因学调查显示4例患者（P1、P2、P4和P5）存在幽门螺杆菌胃炎。当面对假性吸收不良的证据时，患者3、6和7承认不遵守LT4治疗。结论：FT4增高率比LT4吸收率、FT4比值、FT4增高率更能有效鉴别假性吸收不良与吸收不良。然而，进一步的多中心研究涉及更大的样本量将有助于证实这些发现。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Endocrine ENDOCRINOLOGY & METABOLISM-

CiteScore

6.50

自引率

5.40%

发文量

295

审稿时长

1.5 months

期刊介绍： Well-established as a major journal in today’s rapidly advancing experimental and clinical research areas, Endocrine publishes original articles devoted to basic (including molecular, cellular and physiological studies), translational and clinical research in all the different fields of endocrinology and metabolism. Articles will be accepted based on peer-reviews, priority, and editorial decision. Invited reviews, mini-reviews and viewpoints on relevant pathophysiological and clinical topics, as well as Editorials on articles appearing in the Journal, are published. Unsolicited Editorials will be evaluated by the editorial team. Outcomes of scientific meetings, as well as guidelines and position statements, may be submitted. The Journal also considers special feature articles in the field of endocrine genetics and epigenetics, as well as articles devoted to novel methods and techniques in endocrinology. Endocrine covers controversial, clinical endocrine issues. Meta-analyses on endocrine and metabolic topics are also accepted. Descriptions of single clinical cases and/or small patients studies are not published unless of exceptional interest. However, reports of novel imaging studies and endocrine side effects in single patients may be considered. Research letters and letters to the editor related or unrelated to recently published articles can be submitted. Endocrine covers leading topics in endocrinology such as neuroendocrinology, pituitary and hypothalamic peptides, thyroid physiological and clinical aspects, bone and mineral metabolism and osteoporosis, obesity, lipid and energy metabolism and food intake control, insulin, Type 1 and Type 2 diabetes, hormones of male and female reproduction, adrenal diseases pediatric and geriatric endocrinology, endocrine hypertension and endocrine oncology.