title: Effects of thyroid hormone replacement on glycated hemoglobin levels in non diabetic subjects with overt hypothyroidism.
abstract: OBJECTIVE
  Glycated hemoglobin (HbA1c) may not accurately reflect the level of glycemia in conditions of altered erythrocyte turnover. Hypothyroidism is one condition associated with sluggish erythropoesis. To assess changes in HbA1c, independent of changes in plasma glucose after initiation of thyroxine replacement in patients with overt hypothyroidism.
  
  
  METHODS
  In this prospective longitudinal study carried out in a tertiary care centre, adult non-diabetic patients with overt hypothyroidism recruited between March 2012 to August 2013 were rendered euthyroid on thyroxine. They underwent testing for hemoglobin, HbA1c, reticulocyte count, thyroxine, thyrotropin and a standard oral glucose tolerance test, both before and at 3 months after restoration to the euthyroid state. Main outcome assessed was the change in HbA1c independent of the change in glucose parameters.
  
  
  RESULTS
  Thirty eight patients (35 female and 3 male) aged 37.8 ± 10.2 years with overt hypothyroidism (thyroxine 12.6 ± 13.4 ng/mL and thyrotropin -98.1 ± 63.7 µIU/mL respectively) were recruited. While HbA1c fell from 5.8 ± 0.7% to 5.6 ± 0.5% (p = 0.009) at 3 months following the correction of hypothyroidism, there were no changes in the fasting and the 2 hr post oral glucose tolerance test glucose (p = 0.67 and 0.56 respectively). The number of patients with dysglycemia diagnosed by HbA1c (i.e HbA1c ≥ 5.7%) fell from 25 (65.78%) to 17 (44.7%) after treatment (p = 0.008). There were 7 (18.4%) patients with HbA1c ≥ 6.5% at baseline, but this fell to just 4 (10.5%) (p < 0.001) after 3 months of euthyroidism.
  
  
  CONCLUSIONS
  HbA1c is not a reliable diagnostic test for diabetes in the presence of hypothyroidism.
authors.affiliation: Department of Endocrinology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India.
authors.forename: Sailaja
authors.initials: S
authors.lastname: Anantarapu
authors.affiliation: Department of Endocrinology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India.
authors.forename: Suresh
authors.initials: S
authors.lastname: Vaikkakara
authors.affiliation: Department of Endocrinology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India.
authors.forename: Alok
authors.initials: A
authors.lastname: Sachan
authors.affiliation: Department of Pathology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India.
authors.forename: Bobbidi Venkata
authors.initials: BV
authors.lastname: Phaneendra
authors.affiliation: Department of Biochemistry, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India.
authors.forename: Mustur Manohar
authors.initials: MM
authors.lastname: Suchitra
authors.affiliation: Department of Endocrinology, Narayana Medical College, Nellore, Andhra Pradesh, India.
authors.forename: Amaresh Ponnala
authors.initials: AP
authors.lastname: Reddy
authors.affiliation: Department of Endocrinology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India.
authors.forename: Sunil
authors.initials: S
authors.lastname: Epuri
authors.affiliation: Department of Endocrinology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India.
authors.forename: Arun
authors.initials: A
authors.lastname: Mukka
authors.affiliation: Department of Endocrinology, Sri Venkateswara Institute of Medical Sciences, Tirupati, Andhra Pradesh, India.
authors.forename: Dharaneswari
authors.initials: D
authors.lastname: Vemvakam
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D005260:Female; D005951:Glucose Tolerance Test; D006442:Glycated Hemoglobin / Q000032:analysis / Q000187:drug effects*; D020249:Hormone Replacement Therapy; D006801:Humans; D007037:Hypothyroidism / Q000097:blood / Q000188:drug therapy*; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D062606:Tertiary Care Centers; D013974:Thyroxine / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D001786:Blood Glucose; D006442:Glycated Hemoglobin; D013974:Thyroxine