Abstract
INTRODUCTION: The parafollicular cells or clear (C) cells in man are part of neuroendocrine system under Amine Precursor Uptake and Decarboxylation (APUD) cells. Their role in adults has been reputable but in foetus is still unclear. AIM: The present study was a baseline study endeavouring to describe the chronological development of the parafollicular cells with particular focus on its correlation with developing human thyroid follicles. MATERIALS AND METHODS: The study was conducted on 10 aborted foetuses (14-28 weeks), procured from the Department of Obstetrics and Gynaecology, Lok Nayak Hospital, New Delhi, India. Serial sections of foetal thyroid gland were generated, stained with haematoxylin and eosin, and immunohistochemistry using the anticalcitonin antibody and examined qualitatively. RESULTS: In our study, the parafollicular cells were seen as earlier as by 14(th) week. They became morphologically and functionally mature by 16(th) week of gestation. The parafollicular cells were getting organized from scattering to parafollicular location then to a more localized area, i.e., intrafollicular along with the follicular development. As the follicles were enlarging, the intrafollicularly located parafollicular cells which was initially present in groups was getting displaced singly between the follicular cells in the same follicle. CONCLUSION: The sequential development pattern of the parafollicular cells in relation to developing thyroid follicles was established. This immunohistochemical study also concluded that the parafollicular cells might have higher character to play in the early gestational age such as regulation of ossification in the human foetus.