Systematic appraisal of lactose intolerance as cause of increased need for oral thyroxine

Abstract

Context: An increased need for T4 has been described in patients with different gastrointestinal disorders. However, there is a lack of systematic studies assessing the need for T4 in hypothyroid patients with lactose intolerance, a widespread and often occult disorder. Objective: The objective of the study was to assess the replacement T4 dose required in hypothyroid patients with lactose intolerance. Design: This was a cohort study. Setting: The study was conducted at an outpatient endocrinology unit in a University Hospital. Patients: The replacement T4 dose has been analyzed, from 2009 to 2012, in 34 hypothyroid patients due to Hashimoto's thyroiditis and lactose intolerance and being noncompliant with a lactose-free diet. Main Outcome Measure: An individually tailored T4 dose was measured. Results: In all patients with isolated Hashimoto's thyroiditis, target TSH (median TSH 1.02 mU/L) was obtained at a median T4 dose of 1.31 μg/kg/d. In patients with lactose intolerance, only five of 34 patients reached the desired TSH (median TSH 0.83 mU/L) with a similar T4 dose (1.29μg/kg/d). In the remaining 29 patients, the T4 dose was progressively increased and the target TSH (median TSH 1.21 mU/L) was attained at a median T4 dose of 1.81 μg/kg/d (+38%, P < .0001) has been required to attain pharmacological thyroid homeostasis. Conclusions: These findings show that lactose intolerance significantly increased the need for oral T4 in hypothyroid patients. Copyright © 2014 by the Endocrine Society.