title: Cross-sectional area of the median nerve is increased in primary autoimmune hypothyroidism and decreases upon treatment with thyroxine.
abstract: BACKGROUND
  The purpose of this study was to assess changes in the cross-sectional area (CSA) of nervus medianus by ultrasound in newly diagnosed primary hypothyroid patients after thyroxine replacement treatment.
  
  
  METHODS
  The cohort comprised 30 patients with newly diagnosed primary autoimmune hypothyroidism. These were subsequently compared with 30 controls, matched for sex, BMI and age. Ultrasound evaluation, including measurement of CSA at the level of the pisiform bone or tunnel inlet was performed at baseline and after 3months. A CSA threshold of more than 10mm(2) was considered pathological.
  
  
  RESULTS
  CSA was increased in patients compared with controls (9.8±0.7mm(2) vs 7.2±1.1mm(2); P<0.001). Thyroxin substitution increased fT4 levels (baseline, 11.0±0.6pmol/L vs 15.5±0.4pmol/L; P<0.001) and decreased TSH (baseline, 23.9±6.0mIU/L vs 2.7±0.2mIU/L; P<0.001). Thyroxine treatment decreased CSA to 8.4mm(2)±0.3mm(2) (P=0.033). Before treatment, four patients experienced distal paresthesia in the median nerve distribution area. Increased CSA pathognomonic for carpal tunnel syndrome found in two symptomatic patients normalized after 3months. No clinical symptoms were observed after 3months. A positive correlation was found between TSH and CSA (R=0.155, P=0.05) before treatment.
  
  
  CONCLUSIONS
  Our study demonstrates that increase in median nerve CSA caused by primary autoimmune hypothyroidism can be fully reversible after achieving target levels of TSH and fT4.
authors.affiliation: Comenius University Faculty of Medicine5th Department of Internal Medicine, University Hospital, Bratislava, Slovakia danaholovacova@gmail.com.
authors.forename: Dana
authors.initials: D
authors.lastname: Holováčová
authors.affiliation: Comenius University Faculty of Medicine5th Department of Internal Medicine, University Hospital, Bratislava, Slovakia.
authors.forename: Martin
authors.initials: M
authors.lastname: Kužma
authors.affiliation: Comenius University Faculty of Medicine5th Department of Internal Medicine, University Hospital, Bratislava, Slovakia.
authors.forename: Zdenko
authors.initials: Z
authors.lastname: Killinger
authors.affiliation: Comenius University Faculty of Medicine5th Department of Internal Medicine, University Hospital, Bratislava, Slovakia.
authors.forename: Juraj
authors.initials: J
authors.lastname: Payer
mesh_terms: D003430:Cross-Sectional Studies; D005260:Female; D050031:Hashimoto Disease / Q000000981:diagnostic imaging* / Q000188:drug therapy; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000000981:diagnostic imaging* / Q000187:drug effects; D008875:Middle Aged; D013967:Thyroiditis, Autoimmune / Q000000981:diagnostic imaging* / Q000188:drug therapy; D013974:Thyroxine / Q000494:pharmacology / Q000627:therapeutic use*; D016896:Treatment Outcome; D014463:Ultrasonography
chemical_list: D013974:Thyroxine