Levothyroxine absorption test results in patients with TSH elevation resistant to treatment

Şimşir, Ilgın Yıldırım; Soyaltın, Utku Erdem; Özgen, A. Gökhan

doi:10.1007/s12020-019-01889-x

Cited by 13 publications

(5 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The percentage LT4 absorption is calculated using the following formula [ 5 ]: % Absorbed = [increment total T4 (TT4) µg/dL × 10/total administered LT4 µg] × Vd (L) × 100. Increment TT4: peak [TT4] – baseline [TT4].…”

Section: Case Discussionmentioning

confidence: 99%

Levothyroxine absorption test followed by directly observed treatment on an outpatient basis to address long-term high thyrotropin levels in a hypothyroid patient: a case report

et al. 2023

View full text Add to dashboard Cite

Background For the treatment of hypothyroidism, patients are usually placed on lifelong levothyroxine replacement therapy. Achieving clinical and biochemical euthyroid status is sometimes difficult because of several factors, including poor compliance or poor absorption of levothyroxine in the gut mucosa. Case presentation We present the case of a 45-year-old South Asian female with hypothyroidism on lifelong levothyroxine replacement. However, on her multiple follow-up visits over the past 2 years, it was noted that her thyrotropin level was never controlled and was not in range. A thorough history was unyielding in terms of compliance regarding levothyroxine medication and use of over-the-counter pills or mineral supplements that may interfere with the absorption of levothyroxine. Hence, we performed levothyroxine absorption test to rule out any malabsorption as well as document pseudo-malabsorption favoring drug nonadherence. Levothyroxine absorption test resulted in more than 56% absorption of levothyroxine; therefore, the patient was put on weekly directly observed treatment strategy resulting in normalization of thyrotropin levels on successive follow-ups. Conclusion Directly observed treatment to replace levothyroxine once a week can be used as an alternative by health care professionals in patients in whom compliance to daily levothyroxine is the hidden cause of persistently raised thyrotropin. This strategy can reduce undue health burden on the patient and improve adherence to self-medication under confident supervision of the treating physician.

show abstract

Section: Case Discussionmentioning

confidence: 99%

Levothyroxine absorption test followed by directly observed treatment on an outpatient basis to address long-term high thyrotropin levels in a hypothyroid patient: a case report

et al. 2023

View full text Add to dashboard Cite

show abstract

“…Since FT4 and TT4 levels associated highly, even in patients with severe hypothyroidism, FT4 may be used interchangeably with TT4 during LT4AT 5 . In line with this assumption, a recent study revealed that a LT4AT with hourly measurements of FT4 over 6 hours after administration of 1000 μg LT4 is a reliable test to differentiate between true malabsorption and pseudomalabsorption, with more than 60–80% absorption indicating normal absorption 6 . The protocol of another study included administration of LT4 (10 μg/kg body weight or maximum 600 μg) with subsequent measurements of FT4 levels at hourly intervals for 5 hours.…”

mentioning

confidence: 80%

Levothyroxine Absorption Test – An Underused Tool

Müssig

2023

Exp Clin Endocrinol Diabetes

View full text Add to dashboard Cite

“…They were also advised not to take any medications known to affect LT4 absorption (namely proton pump inhibitor, ferrous salts, calcium carbonate, laxatives) at least 24 h prior to the test. Our current LT4AT protocol was derived from previous publications and is based on a 6-h test following 1000 µg of oral LT4 intake ( 9 , 10 , 11 ). At the patient’s admission, a peripheral i.v.…”

Section: Methodsmentioning

confidence: 99%

Levothyroxine malabsorption or pseudomalabsorption? A question in the management of refractory hypothyroidism

Monteiro

Santos

Lopes

et al. 2022

Endocrine Connections

View full text Add to dashboard Cite

Purpose: The levothyroxine absorption test (LT4AT) is an important tool for distinguishing hypothyroidism due to malabsorption from “pseudomalabsorption” conditions. Our aim was to review our institution’s LT4AT results and assess its role in the management of patients with refractory hypothyroidism. Methods: We performed a retrospective study of all patients evaluated for refractory hypothyroidism who underwent LT4AT in our tertiary center between 2014 to 2020. Its results and the impact on thyroid function management during follow-up were assessed. Results: Ten female patients were included with a mean age of 40 years (min-max: 26-62). Mean weight was 72kg (min-max: 43-88) and baseline LT4 dosage ranged from 2.5 to 5.3µg/kg per day. Most common cause of hypothyroidism were postsurgical in 50% (n=5) and autoimmune in 20% (n=2). During LT4AT, normal LT4 absorption was found in all but one individual (mean FT4 increase of 231%, min-max: 85-668). The only patient with objective LT4 absorption impairment (maximal increase of 48% by hour 5) presented also Helicobacter pylori gastritis and prior history of “intestinal surgery” during childhood. No adverse events were reported during any of the LT4ATs. During follow-up [median 11.5 months (IQR 23)], 3 patients obtained euthyroidism and 6 had improved their hypothyroidism state. Conclusions: The LT4AT is an effective and safe way to assess refractory hypothyroidism and provides valuable information to distinguish LT4 malabsorption from “pseudomalabsorption”. Our data suggest that most patients with suspicious LT4 malabsorption perform normally during LT4AT. This test provides relevant information for better management of patients with refractory hypothyroidism.

show abstract

Levothyroxine absorption test results in patients with TSH elevation resistant to treatment

Cited by 13 publications

References 16 publications

Levothyroxine absorption test followed by directly observed treatment on an outpatient basis to address long-term high thyrotropin levels in a hypothyroid patient: a case report

Levothyroxine absorption test followed by directly observed treatment on an outpatient basis to address long-term high thyrotropin levels in a hypothyroid patient: a case report

Levothyroxine Absorption Test – An Underused Tool

Levothyroxine malabsorption or pseudomalabsorption? A question in the management of refractory hypothyroidism

Contact Info

Product

Resources

About