title: Genetic and environmental influence on thyroid gland volume and thickness of thyroid isthmus: a twin study.
abstract: OBJECTIVE
  Decreased thyroid volume has been related to increased prevalence of thyroid cancer.
  
  
  METHODS
  One hundred and fourteen Hungarian adult twin pairs (69 monozygotic, 45 dizygotic) with or without known thyroid disorders underwent thyroid ultrasound. Thickness of the thyroid isthmus was measured at the thickest portion of the gland in the midline using electronic calipers at the time of scanning. Volume of the thyroid lobe was computed according to the following formula: thyroid height*width*depth*correction factor (0.63).
  
  
  RESULTS
  Age-, sex-, body mass index- and smoking-adjusted heritability of the thickness of thyroid isthmus was 50% (95% confidence interval [CI], 35 to 66%). Neither left nor right thyroid volume showed additive genetic effects, but shared environments were 68% (95% CI, 48 to 80%) and 79% (95% CI, 72 to 87%), respectively. Magnitudes of monozygotic and dizygotic co-twin correlations were not substantially impacted by the correction of covariates of body mass index and smoking. Unshared environmental effects showed a moderate influence on dependent parameters (24-50%).
  
  
  CONCLUSIONS
  Our analysis support that familial factors are important for thyroid measures in a general twin population. A larger sample size is needed to show whether this is because of common environmental (e.g. intrauterine effects, regional nutrition habits, iodine supply) or genetic effects.
authors.affiliation: Department of Radiology and Oncotherapy, Semmelweis University, Budapest, Hungary.
authors.forename: Adam Domonkos
authors.initials: AD
authors.lastname: Tarnoki
authors.affiliation: Department of Radiology and Oncotherapy, Semmelweis University, Budapest, Hungary.
authors.forename: David Laszlo
authors.initials: DL
authors.lastname: Tarnoki
authors.affiliation: Department of Medicine, Policlinic of Hospitaller Brothers of St. John of Good, Budapest, Hungary.
authors.forename: Gabor
authors.initials: G
authors.lastname: Speer
authors.affiliation: Central European University, Budapest, Hungary.
authors.forename: Levente
authors.initials: L
authors.lastname: Littvay
authors.affiliation: Department of Radiology and Oncotherapy, Semmelweis University, Budapest, Hungary.
authors.forename: Pal
authors.initials: P
authors.lastname: Bata
authors.affiliation: Houston Methodist DeBakey Heart & Vascular Center,, The Houston Methodist Hospital, Houston, TX, USA.
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Garami
authors.affiliation: Department of Radiology and Oncotherapy, Semmelweis University, Budapest, Hungary.
authors.forename: Viktor
authors.initials: V
authors.lastname: Berczi
authors.affiliation: Department of Radiology and Oncotherapy, Semmelweis University, Budapest, Hungary.
authors.forename: Kinga
authors.initials: K
authors.lastname: Karlinger
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D005260:Female; D059647:Gene-Environment Interaction; D020022:Genetic Predisposition to Disease / Q000453:epidemiology; D006801:Humans; D006814:Hungary / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009929:Organ Size / Q000235:genetics; D015995:Prevalence; D018570:Risk Assessment; D013961:Thyroid Gland / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D014429:Twins, Dizygotic / Q000235:genetics; D014430:Twins, Monozygotic / Q000235:genetics; D014463:Ultrasonography