title: Thyroid function and insulin sensitivity before and after bilio-pancreatic diversion.
abstract: BACKGROUND
  Bilio-pancreatic diversion (BPD) induces permanent weight loss in previously severe obese patients through a malabsorptive mechanism. The aim of the study was to evaluate the modifications of circulating thyroid hormones after BPD, a surgical procedure which interferes with the entero-hepatic circulation of biliary metabolites.
  
  
  METHODS
  Forty-five patients were studied before and 2 years after BPD. Thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4), anti-thyroid antibodies, iodine urinary excretion, lipid profile, insulin and glucose plasma levels were assessed. The insulin-resistance HOMA IR index was calculated, and colour Doppler ultrasonography of the neck was performed.
  
  
  RESULTS
  The subjects (23%) had subclinical hypothyroidism prior to BPD (TSH levels above the normal range with normal fT3 and fT4 levels). After 2 years 40.42% of the population showed subclinical hypothyroidism, while 6.3% became frankly hypothyroid, all of them with no evidence of auto-immune thyroiditis. Most of the patients, who became sub-clinically hypothyroid only following BPD, had already thyroid alterations at the sonogram (multi-nodular euthyroid goiter and thyroidal cysts) prior to surgery.
  
  
  CONCLUSIONS
  BPD increases the prevalence of subclinical or even frank hypothyroidism, without causing a defect in thyroid function itself, through several integrated mechanisms. (1) It induces iodine malabsorption, which is partially compensated by iodine excretion contraction. (2) The entero-hepatic open circulation determines fT3 loss, which induces subclinical or frank hypothyroidism in patients with pre-existing thyroid alterations, interfering also with the weight loss progress. Iodine supplementation should be recommended in those patients reporting thyroid alterations at the sonogram prior to BPD, LT4 therapy should be strictly monitored in patients suffering of subclinical hypopthiroidism and T3 therapy should eventually be considered for patients diagnosed with frank hypothyroidism prior to BPD.
authors.affiliation: Department of Internal Medicine and Diabetes Center, Catholic University, L.go Gemelli 8, 00168 Rome, Italy. dgniuli@gmail.com
authors.forename: Donatella
authors.initials: D
authors.lastname: Gniuli
authors.forename: Laura
authors.initials: L
authors.lastname: Leccesi
authors.forename: Caterina
authors.initials: C
authors.lastname: Guidone
authors.forename: Amerigo
authors.initials: A
authors.lastname: Iaconelli
authors.forename: Chiara
authors.initials: C
authors.lastname: Chiellini
authors.forename: Andrea
authors.initials: A
authors.lastname: Manto
authors.forename: Marco
authors.initials: M
authors.lastname: Castagneto
authors.forename: Giovanni
authors.initials: G
authors.lastname: Ghirlanda
authors.forename: Geltrude
authors.initials: G
authors.lastname: Mingrone
mesh_terms: D000328:Adult; D015904:Biliopancreatic Diversion; D001823:Body Composition; D005260:Female; D006801:Humans; D007037:Hypothyroidism / Q000209:etiology / Q000503:physiopathology; D007333:Insulin Resistance / Q000502:physiology*; D008102:Liver Circulation / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000503:physiopathology* / Q000601:surgery*; D011184:Postoperative Period; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000503:physiopathology*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D018615:Ultrasonography, Doppler, Color
chemical_list: D014284:Triiodothyronine; D013972:Thyrotropin; D013974:Thyroxine