title: Size and location of thyroid gland in the fetal period.
abstract: OBJECTIVE
  The present study's purpose was to examine the size and location of the thyroid gland using anatomic dissection methods on fetal cadavers.
  
  
  METHODS
  This study was performed on 200 spontaneously aborted human fetuses (100 males and 100 females) aged between 9 and 40 weeks of gestation. Fetuses without any external and internal pathology or anomaly were included in this study. Fetuses were divided into four groups based on gestational ages as follows: first group 9-12 weeks (first trimester), second group 13-25 weeks (second trimester), third group 26-37 weeks (third trimester) and fourth group 38-40 weeks (full term). The fetuses were also grouped into monthly cohorts as follows: 9-12 weeks, 3rd month; 13-16 weeks, 4th month; 17-20 weeks, 5th month; 21-24 weeks, 6th month; 25-28 weeks, 7th month; 29-32 weeks, 8th month; 33-36 weeks, 9th month; and 37-40 weeks, 10th month. The anterior necks of fetuses were dissected and the thyroid glands exposed. Vertebral and laryngeal levels and the dimensions (width, length, thickness and weight) of the fetal thyroid glands were determined by anatomical dissection methods. The dimensions and ratios of the fetal thyroid gland (weight/fetal body weight) were evaluated.
  
  
  RESULTS
  The mean values and standard deviations of all parameters by gestational weeks, months, and trimesters were calculated. It was found that all parameters increased with gestational age. No significant differences were observed between genders in all parameters (P > 0.05). There were no significant differences between the right and the left sides for parameters of the thyroid glands. The levels of the superior poles of the thyroid lobes were located at the cervical (C) C1-C3 vertebral bodies. The levels of the inferior poles of the thyroid lobes were located at C4-C5 vertebral bodies. The levels of the superior poles of thyroid lobes were located between the upper ½ and lower ½ of the thyroid cartilage or cricoid cartilage. The levels of the inferior poles of the thyroid lobes were located between the second and sixth tracheal rings. The distance between the superior poles of the thyroid gland and the hyoid bone increased throughout the fetal period. The dimensions of fetal thyroid glands increased with gestational age. The ratio between thyroid gland weights and fetal body weights was unchanged during the fetal period.
  
  
  CONCLUSIONS
  We believe that the results obtained from this study will be useful in monitoring thyroid glands in the intrauterine period as well as recognizing early diagnosis and treatment of thyroid anomalies. It will also contribute to future studies in obstetrics, perinatology, and fetopathology.
authors.affiliation: Department of Anatomy, Faculty of Medicine, Süleyman Demirel University, 32260, Isparta, Turkey, ozgunerg@hotmail.com.
authors.forename: Gülnur
authors.initials: G
authors.lastname: Ozguner
authors.forename: Osman
authors.initials: O
authors.lastname: Sulak
mesh_terms: D002102:Cadaver; D004210:Dissection; D005260:Female; D005333:Fetus; D005865:Gestational Age; D006801:Humans; D008297:Male; D009929:Organ Size; D013961:Thyroid Gland / Q000196:embryology*
references.citation: Saudi Med J. 2007 Apr;28(4):524-8
references.pmid: 17457471
references.citation: Ultrasound Obstet Gynecol. 2009 Apr;33(4):412-20
references.pmid: 19306478
references.citation: Nucl Med Commun. 1984 Mar;5(3):163-8
references.pmid: 6099530
references.citation: Folia Morphol (Warsz). 2010 Feb;69(1):47-50
references.pmid: 20235050
references.citation: Clin Endocrinol (Oxf). 1998 Mar;48(3):259-64
references.pmid: 9578813
references.citation: Surg Radiol Anat. 2004 Apr;26(2):91-5
references.pmid: 14615915
references.citation: Prenat Diagn. 2003 Sep;23(9):740-2
references.pmid: 12975785
references.citation: Folia Morphol (Warsz). 2011 May;70(2):103-8
references.pmid: 21630231
references.citation: J Ultrasound Med. 2001 Jun;20(6):613-7
references.pmid: 11400935
references.citation: Biol Neonate. 1989;55(6):376-85
references.pmid: 2663092
references.citation: Eur Arch Otorhinolaryngol. 2011 Sep;268(9):1357-63
references.pmid: 21298390
references.citation: Singapore Med J. 2008 Oct;49(10):831-4
references.pmid: 18946620
references.citation: J Clin Ultrasound. 2008 May;36(4):193-9
references.pmid: 18286516
references.citation: Chir Ital. 2008 Jan-Feb;60(1):41-6
references.pmid: 18389746
references.citation: Ultrasound Obstet Gynecol. 1998 Feb;11(2):118-22
references.pmid: 9549838
references.citation: Surg Radiol Anat. 2010 Aug;32(7):675-81
references.pmid: 20454794
references.citation: Mymensingh Med J. 2008 Jan;17(1):8-13
references.pmid: 18285723
references.citation: Surg Radiol Anat. 2007 Feb;29(1):21-7
references.pmid: 17146601