These posters in the upcoming meeting of the ATA indicate the increased need for T4 for patients with GI problems.
Poster 1
Main Causes of Thyroxine Malabsorption The Systematic Study
C Virili et al.
Despite the increasing attempt to individualize the levothyroxine (T4) treatment, a significant fraction of the treated patients does not reach the target TSH. Previous studies showed that several gastro- intestinal (GI) disorders may increase the need for T4. This study was aimed at analyzing, in a large cohort of consecutively examined patients, the prevalence of the more relevant causes of increased need for T4 and at quantifying the impact of these disorders on the T4 requirement. A total of 2808 patients with hypothyroidism, due to inflammatory or autoimmune thyroiditis, were prospectively treated with a tight schedule and were followed up for at least 24 months. All patients agreed to take thyroxine in fasting conditions, waiting at least one hour before eating or drinking. Some 499 (17,7%) patients in pregnancy, lactating, obese, using foods and/or cosmetics and drugs known to affect T4 bioavailability, were positively excluded. The dose has been increased until the desired serum TSH (0.5- 2.5mU/l) had been obtained. Patients have been divided in re- sponders and non-responders based on the threshold dose (1.21 lg/ Kg BW/day) obtained as median requirement in 208 hypothyroid patients in whom interferences with T4 treatment, including GI disorders, had been excluded. After all, 295/2309 (12.8%) patients (268W/27M; median age=50 years; median BMI=25.37) failed to reach the target TSH and were classified as non responders. The median dose to attain target TSH in these patients was higher than in reference group (1.52 vs 1.21 lg/Kg BW/day; p < 0.0001). They underwent diagnostic workup for gastrointestinal disorders which revealed lactose intolerance in 38 patients (12,8%), H pilory infec- tion and related nonatrophic gastritis in 123 patients (42%), a celiac disease in 10 patients (3.4%), a gastric atrophy in 48 patients (16.3%) and other causes in 27 patients. A definite diagnosis was not reached in 49 patients (16.6%). The median need for T4 ranged from 1.45 lg/ Kg BW/day in H pylori related disorders to 1.76 lg/Kg BW/day in celiac patients. These data clearly indicate that GI disorders, mostly occult, account for a significant fraction of T4-treated patients with refractory hypothyroidism.
Poster 2
Ulcerative Colitis in Thyroid Disorders: Evidence for an increased need for thyroxine
C Virilli et al
Data on the association of ulceratie colitis (UC), a chronic inflam- matory disorder of the large bowel, and thyroid disorders are scarce and whether the presence of UC may interfere with thyroxine (T4) treatment efficacy is not known. The aim of this study has been to examine, in a large cohort of consecutively examined patients with thyroid disorders, the presence of UC and its role in the pharmaco- logic thyroid homeostasis. A total of 8537 patients were retrospec- tively analyzed and 43 patients bearing an inflammatory bowel disease were recruited (0.005%). Among them, 32 patients had UC (28F/4M; median age = 59 years), and 15 of them (F/M; median age = 60 years) were in need for T4 treatment. All patients have pledged to take thyroxine in fasting conditions, abstaining from eating or drinking for at least one hour. T4 was prescribed in an increasing fashion until the target TSH (<0.8-2.5> mU/l) has been attained and maintained in at least 2 controls. To calculate the pos- sible excess of T4 required in UC patients, the requirement of T4 has been compared to the one observed in 115, similarly treated, age- and BMI-matched patients, clearly devoid from gastrointestinal and/or pharmacological interference. The median thyroxine dose required was 1.72 lg/kg/day, significantly higher than in the reference group (+22%). An higher dose was needed in 13 out of 15 UC patients (87%). Since half of these were senior patients, we divided the sample in two groups: under 60 years (7 patients; median age = 53 years) and over 60 years (8 patients; median age = 73 years). In younger patients a dose excess has been detected in 5 out of 7 patients (median T4 increase = +26%) being the median T4 requirement 1.78lg/kg/day, significantly increased as compared to reference patients (1.31 lg/kg/day; p = 0.003). In the elderly group an increased T4 dose was seen in all 8 patients (median T4 increase = +21%), again significantly higher than the one required by the age-matched reference group (p = 0.019). The increased need for thyroxine was therefore similar independently from the age of patients. Our findings support the hypothesis that ulcerative colitis may represent a novel cause of increased need for thyroxine.
