title: Glucose turnover, fuel oxidation and forearm substrate exchange in patients with thyrotoxicosis before and after medical treatment.
abstract: OBJECTIVE
  Accelerated metabolism is a hallmark of thyrotoxicosis, but the underlying biochemical mechanisms are incompletely understood and the majority of studies have investigated normal subjects rendered only modestly hyperthyroid for a brief period of time. We have therefore studied a group of thyrotoxic patients using several different techniques.
  
  
  METHODS
  Twelve patients with newly diagnosed diffuse (10 patients) or nodular (2 patients) toxic goitre (10 women, 2 men; age 42.8 +/- 3.2 years; BMI 21.6 +/- 0.7 kg/m2) before ('pretreatment') and after ('treated') 11.2 +/- 1.0 weeks treatment with methimazole and compared these patients to a control group ('control') of 11 subjects (9 women, 2 men; age 40.5 +/- 3.9 years; BMI 22.5 +/- 1.0 kg/m2). All were studied for 3 hours in the basal state, using indirect calorimetry, isotope dilution for the measurement of glucose turnover and the forearm technique for assessment of muscle metabolism.
  
  
  RESULTS
  Prior to treatment patients with thyrotoxicosis were characterized by increased (P < 0.05) levels of T3 (3.75 +/- 0.23 nmol/l (pretreatment), 1.89 +/- 0.08 (treated) and 1.75 +/- 0.11 (control)), resting energy expenditure (130.5 +/- 3.5 (pretreatment), 107.7 +/- 2.7 (treated) and 106.3 +/- 3.1 (control), % of predicted), protein oxidation (0.67 +/- 0.03 (pretreatment), 0.54 +/- 0.06 (treated) and 0.46 +/- 0.05 (control), mg/kg/min), lipid oxidation (1.34 +/- 0.08 (pretreatment), 1.00 +/- 0.06 (treated) and 1.02 +/- 0.04 (control), mg/kg/min), endogenous glucose production (2.51 +/- 0.13 (pretreatment), 1.86 +/- 0.12 (treated) and 1.85 +/- 0.12 (control), mg/kg/min), non-oxidative glucose turnover (1.28 +/- 0.16 (pretreatment), 0.75 +/- 0.18 (treated) and 0.71 +/- 0.11 (control), mg/kg/min) and a 50% increase in total forearm blood flow. Glucose oxidation (1.23 +/- 0.09 (pretreatment), 1.13 +/- 0.10 (treated) and 1.21 +/- 0.11 (control) mg/kg/min), exchange of substrates in the muscles of the forearm and circulating levels of insulin, C-peptide, growth hormone or glucagon were not influenced by hyperthyroidism. Propranolol (20 mg thrice daily) given to 7 of the patients for 2 days did not affect circulating levels of thyroid hormones, energy expenditure or glucose turnover rates.
  
  
  CONCLUSIONS
  These results suggest that all major fuel sources contribute to the hypermetabolism of thyrotoxicosis and that augmented non-oxidative glucose metabolism may further aggravate the condition. All abnormalities diminish with medical treatment of the disease.
authors.affiliation: Medical Department M (Endocrinology & Diabetes), Aarhus Kommunehospital, Denmark.
authors.forename: N
authors.initials: N
authors.lastname: Møller
authors.forename: S
authors.initials: S
authors.lastname: Nielsen
authors.forename: B
authors.initials: B
authors.lastname: Nyholm
authors.forename: N
authors.initials: N
authors.lastname: Pørksen
authors.forename: K G
authors.initials: KG
authors.lastname: Alberti
authors.forename: J
authors.initials: J
authors.lastname: Weeke
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000328:Adult; D013956:Antithyroid Agents / Q000627:therapeutic use*; D002153:Calorimetry, Indirect; D004359:Drug Therapy, Combination; D005260:Female; D005542:Forearm; D005947:Glucose / Q000378:metabolism*; D006042:Goiter / Q000097:blood / Q000188:drug therapy / Q000378:metabolism*; D006801:Humans; D008297:Male; D008713:Methimazole / Q000627:therapeutic use*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D011433:Propranolol / Q000627:therapeutic use; D011865:Radioisotope Dilution Technique; D012039:Regional Blood Flow / Q000187:drug effects; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D000319:Adrenergic beta-Antagonists; D013956:Antithyroid Agents; D014284:Triiodothyronine; D008713:Methimazole; D013972:Thyrotropin; D011433:Propranolol; D005947:Glucose; D013974:Thyroxine