Dr. Sushant Swaroop Das Dr. J. M. Kaul Dr. Sabita Mishra DEVELOPMENT OF PARAFOLLICULAR CELLS AND ITS RELATIONSHIP WITH DEVELOPING THYROID FOLLICLES IN HUMAN FETUSES Dr. Sushant Swaroop Das Dr. J. M. Kaul Dr. Sabita Mishra Department of Anatomy Maulana Azad Medical College and associated Lok Nayak, G.N.E.C., G. B. Pant Hospitals. New Delhi-110002

INTRODUCTION

AIMS AND OBJECTIVES To study the development of parafollicular cells of thyroid gland in relation to thyroid follicles by light microscopy in human fetuses. Past studies- Thyroid follicles and PF cells - single entities. Present study- to correlate. To study the time of appearance of neurosecretory granules in parafollicular cells at various gestational weeks. To study the expression of anti-calcitonin antibody in parafollicular cells by IHC at at various gestational weeks.

MATERIALS AND METHODS STUDY DESIGN: Descriptive study STUDY POPULATION: a) 10 aborted fetuses at various stages of gestation. b) Fetuses procured from the Dept. of Obstetrics and Gynaecology, LN Hospital, New Delhi. c) Written informed consent of the parents and institutional ethical clearance taken. INCLUSION CRITERIA:- All normal fetuses EXCLUSION CRITERIA:- Macerated fetuses Putrefied fetuses Fetuses with any congenital abnormalities The gestational ages of the fetuses determined by using the following parameters: - Crown –Heel length Crown-Rump length Bi-parietal diameter Foot length Weight

PROCESSING:- STAINING METHODS:- The fetuses immediately fixed in 10% buffered neutral formalin. Thyroid gland identified and dissected. The thyroid tissue processed in paraffin. 6µm sections generated in a rotary microtome and stained. STAINING METHODS:- Haematoxylin and eosin staining to see the morphology and relations of the parafollicular cells to the thyroid follicles. Sevier-Munger stain to identify the neurosecretory granules in PF cells. Immunohistochemistry with anti calcitonin antibody- a specific marker to identify the parafollicular cells more precisely. Sections were seen under BX61 Olympus microscope and analysed by image pro plus software. Images were captured by Olympus DP 71 digital camera.

OBSERVATIONS

H&E 14 wks 18 wks 15µm 100µm 15µm 27 wks 23 wks 100µm 15µm

Sevier Munger Stain 14 wks 18 wks 15µm 28 wks 100µm 15µm

Anti- calcitonin antibody Peptide hormone of 32 amino acids. Specific marker – PF cells. Rabbit Polyclonal antibody. 14 wks 100µm

IHC 15 wks 16 wks 15µm 15µm 23 wks 28 wks 15µm 15µm

DISCUSSION

CONCLUSION & SUMMARY In our study, the PF cells were seen as earlier as 14th week. They became morphologically and functionally mature by 16th week of gestation. It can be concluded from our study that the PF cells are getting organized from scattering to parafollicular location then to a more localized area i.e. intrafollicular along with the follicular development. As the follicles are enlarging, the intrafollicularly located PF cells which were initially present in groups are getting displaced singly between the follicular cells in the same follicle. Also the decrease in the intensity of immunostain of the thyroid parenchyma might indicate the decrease in the calcitonin content of developing thyroid gland as the gestational age advances. Thus it may be concluded that calcitonin has a higher role to play in the early gestational age. This finding may prove a milestone in finding the role of calcitonin in the developing fetus. As calcitonin inhibits osteoclastic activity and increase osteoblasts numbers, it supports the hypothesis that it might play a contributing factor in the regulation of ossification in the human fetus. These findings could be further correlated with electron microscopic study of developing PF cells to find the cause of such organization.

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