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

J Clin Endocrinol Metab. 2014 Aug;99(8):E1454-8. doi: 10.1210/jc.2014-1217. Epub 2014 May 5.


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 (1.29 μg/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). In six of these patients, other gastrointestinal disorders were diagnosed, and their median T4 requirement was higher (2.04 μg/kg/d; +55%; P = .0032). In the remaining 23 patients with isolated lactose intolerance, a median T4 dose of 1.72 μg/kg/d (+31% 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.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Oral
  • Adolescent
  • Adult
  • Cohort Studies
  • Diet, Carbohydrate-Restricted
  • Dose-Response Relationship, Drug
  • Drug Dosage Calculations
  • Female
  • Hashimoto Disease / blood
  • Hashimoto Disease / complications
  • Hashimoto Disease / drug therapy
  • Hormone Replacement Therapy
  • Humans
  • Hypothyroidism / blood
  • Hypothyroidism / complications*
  • Hypothyroidism / drug therapy*
  • Lactose Intolerance / complications*
  • Male
  • Middle Aged
  • Patient Compliance / statistics & numerical data
  • Thyroxine / administration & dosage*
  • Young Adult


  • Thyroxine