title: Glucose tolerance and lipid profile in longterm exogenous subclinical hyperthyroidism and the effects of restoration of euthyroidism, a randomised controlled trial.
abstract: OBJECTIVE
  The impact of prolonged subclinical hyperthyroidism on glucose and lipid metabolism is unclear. Therefore, we evaluated glucose and lipid metabolism in patients with differentiated thyroid carcinoma (DTC) on TSH suppressive thyroxine therapy as a model for subclinical hyperthyroidism and investigated whether restoration to euthyroidism affects metabolism.
  
  
  METHODS
  We performed a prospective, single-blinded, placebo-controlled, randomised trial of 6 months duration with 2 parallel groups.
  
  
  METHODS
  Twenty-five subjects with a history of differentiated thyroid carcinoma with > 10 years TSH-suppressive therapy with l-thyroxine completed the study. l-thyroxine dose was replaced by study medication containing l-thyroxine or l-thyroxine plus placebo. Medication was titrated to establish continuation of TSH suppression (low-TSH group, 13 patients) and euthyroidism (euthyroidism group, 12 patients).
  
  
  METHODS
  We evaluated glucose metabolism by glucose tolerance test and HOMA (IR) and lipid metabolism by lipid profile. In addition, we measured plasma concentrations of glucoregulatory hormones.
  
  
  RESULTS
  At baseline, glucose tolerance, HOMA (IR), lipid profile and plasma concentrations of glucoregulatory hormones were within the normal range. No significant differences between the low TSH and euthyroidism group were observed. After 6 months, neither glucose nor lipid metabolism in the low TSH group were different from baseline values.
  
  
  CONCLUSIONS
  In summary, glucose and lipid metabolism in patients with DTC and long-term subclinical hyperthyroidism in general are not affected. Restoration of euthyroidism in general does not affect glucose and lipid metabolism.
authors.affiliation: Department of Endocrinology and Metabolism, Leiden university medical Centre, Leiden, the Netherlands.
authors.forename: K A
authors.initials: KA
authors.lastname: Heemstra
authors.forename: J W A
authors.initials: JW
authors.lastname: Smit
authors.forename: C F A
authors.initials: CF
authors.lastname: Eustatia-Rutten
authors.forename: A C
authors.initials: AC
authors.lastname: Heijboer
authors.forename: M
authors.initials: M
authors.lastname: Frölich
authors.forename: J A
authors.initials: JA
authors.lastname: Romijn
authors.forename: E P M
authors.initials: EP
authors.lastname: Corssmit
mesh_terms: D000328:Adult; D002277:Carcinoma / Q000097:blood / Q000188:drug therapy / Q000601:surgery; D005260:Female; D018149:Glucose Intolerance; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood*; D007328:Insulin / Q000097:blood; D008055:Lipids / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D016037:Single-Blind Method; D013964:Thyroid Neoplasms / Q000097:blood / Q000188:drug therapy / Q000601:surgery; D013965:Thyroidectomy; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood / Q000627:therapeutic use*
chemical_list: D007328:Insulin; D008055:Lipids; D013972:Thyrotropin; D013974:Thyroxine