Morphometry and Histology of Thyroid Gland in Developing Human Foetuses: A Cross-sectional Study

Abstract

Introduction: The thyroid gland regulates the basal metabolic rate, somatic growth, and physical growth. The thyroid gland plays a major role in the normal growth of a foetus during the prenatal period. There are few literatures on foetal thyroid gland. Aim: To study the various morphometric and histological changes during intrauterine life in both gender of human foetuses. Materials and Methods: This cross-sectional study was carried out in the Department of Obstetrics and Gynaecology, Dr. Sushila Tiwari Hospital Government Medical College, Haldwani (UK) and Saraswati Medical College, Unnao in the period of August 2015-2022. Government Medical College, Haldwani for duration of three years on medically terminated 70 foetus of both sexes of known gestational age ranging from 10 to 40 weeks. These foetuses were divided among three groups as group 1 (10-20 weeks), group 2 (21-30 weeks), group 3 (31- 40 week). Midline dissection of neck was done to expose the thyroid gland. Morphometric parameters like length, width, and thickness of each lobe and the isthmus were measured by digital Vernier caliper, weight was also taken by digital weighing machine, then tissue processing was done and paraffin blocks were prepared. All sections were stained with Haematoxylin and Eosin stain (H&E) and studied under the microscope aided camera. By using Analysis of Variance (ANOVA) test and Independent sample test (t-test) comparison among different age groups and gender has been done. Results: There was a significant increase in foetal thyroid weight, length and widths of the right and left lobes, and length of the isthmus with increase in gestational age, while no significant relation was found between male and female foetuses of measured morphometric parameter. The histological features revealed that development of thyroid gland starts earlier and thin capsule was seen at 12 week and it became thicker and more vascular till 35 weeks. Follicles started to form at 14 week and matured follicle were seen at the age of 24 weeks, at 25th week, the lining epithelium of follicles was low columnar to cuboidal, colloid material was seen almost in every follicle. C cells were found at 22 weeks. At the 36 weeks, the follicles were seen spherical and reached to maturity level. Conclusion: As the gestational age increases, the morphometric parameters must increase, if not so, it means the growth of gland is hampered. The knowledge of the growth and differentiation of foetal thyroid will be helpful for clinicians, to judge the thyroid structure prenatally.