Although this paper has a publication date of almost a year ago, I have only just noticed it.
The results of the study do not seem surprising but, as always, it is essential that the work is performed - otherwise we are just making assumptions.
Levothyroxine treatment and gastric juice pH in humans: the proof of concept.
Virili C1, Bruno G2, Santaguida MG3, Gargano L3, Stramazzo I1, De Vito C4, Cicenia A2, Scalese G2, Porowska B5, Severi C2, Centanni M1
Endocrine, 27 Apr 2022, 77(1):102-111
DOI: 10.1007/s12020-022-03056-1 PMID: 35477833 PMCID: PMC9242941
Abstract
Purpose
Despite the absorption of oral thyroxine (T4) occurs in the small bowel, several patients with gastric disorders show an increased need for T4. In vitro evidence suggested that medium pH variations interfere with T4 dissolution. This study was aimed at finding the proof of concept of a direct relationship between the minimal effective dose of T4 and the actual gastric juice pH.
Patients and methods
Among 311 consecutively thyroxine-treated patients, 61 bearing Hashimoto's thyroiditis (52 F/9 M; median age = 51 years) who complained persistent dyspepsia and/or upper abdominal symptoms following a noninvasive workup for gastrointestinal disorders, underwent EGDS with multiple biopsies and gastric juice pH measurement. All patients accepted to take thyroxine in fasting conditions, abstaining from eating or drinking for one hour.
Results
Thyroxine requirement increased along with the rising gastric pH (ρ = 0.4229; p = 0.0007). A multivariate analysis revealed that gastric pH was, beside body mass index, the far more important independent variable in determining the effective dose of T4 (p = 0.001). The ROC curve revealed that the pH threshold for an increased thyroxine requirement was at 2.28, being the AUC by 78%. Subdividing patients by the histologic findings, it appeared a significant increase (p = 0.0025) along with the progressive damage of gastric mucosa.
Conclusion
The in vivo measurement of gastric pH highlighted its key role in determining the minimal effective dose of oral T4 and may explain the interference of food, of some drugs and gut disorders on levothyroxine treatment.
Full paper freely accessible here: