Increased need for thyroxine has been described in several gastrointestinal disorders (H. pylori infection, gastric atrophy, celiac disease), even in their occult or symptomless forms. A transitory or stable impairment of gastric acidity, by increasing pH value, seems to interfere with thyroxine availability, highlighting a novel role for the stomach in the following intestinal T4 absorption. Distinctive dissolution profiles of different T4 preparations (tablets and/or softgel capsules) have been described and softgel T4 capsules performed better than tablets in alkaline pH. In patients with gastric disorders, where larger doses of thyroxine tablets are required, softgel capsules of T4 may help to reach the therapeutic target and this represented the aim of our study. To this end, we have enrolled patients in therapeutic thyroid homeostasis, presenting with impaired gastric acid secretion and longlasting T4 treatment (>5 years) with the same brand of tablets. All these patients had been advised and agreed to take oral thyroxine under fasting conditions, waiting at least 1 h before eating. Patients bearing additional conditions interfering with thyroxine treatment (e.g. drugs, intestinal disorders, pregnancy, etc.) were excluded from the study. A total of 30 patients (28F/2M; median age=51 years; median T4 dose=2.05 μg/kg per day) met these criteria and switched from the usual tablets treatment to the softgel T4 capsules at a significantly lower dose of thyroxine (median T4 dose=1.77 μg/kg per day; P=0.0082). Thyroid function and TSH were measured after 3, 6, 12 and 18 months from the treatment switch. Most of patients (18/30; 60%) showed a TSH increase after 3 months of treatment, with no change in FT4 levels. However, after 6 months, TSH returned to the baseline values in about 2/3 of patients despite the reduced dose of T4. Thyroid hormones were not changed during the study (P=NS). These preliminar findings strongly suggest that treatment with softgel T4 capsules may reach the therapetic goal at a lower dose than a T4 tablet preparation in patients with impaired gastric acid secretion.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.
05 - 09 May 2012
European Society of Endocrinology