International Journal of Anatomy and Research

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Type of Article: Original Research

Year: 2016 | Volume 4 | Issue 2 | Page No. 2386-2391

Date of Publication: 31-05-2016



Archana Belavadi Jagadish *1, Pradeep Prabhakar 2, Lakshmi Prabha Subhash R 3.


*1 Assistant Professor, Department of Anatomy, Sri Siddhartha Medical College, Tumkur, Karnataka, India.

2 Senior Resident, Department of Orthopaedics, Sri Siddhartha Medical College, Tumkur, Karnataka, India.

3 Professor and Head, Department of Anatomy, Sri Siddhartha Medical College, Tumkur, Karnataka, India.

Address: Dr Archana Belavadi Jagadish, Assistant Professor, Department of Anatomy, Sri Siddhartha Medical College, Tumkur, Karnataka, India.


Background: The thyroid is a highly vascular endocrine gland with two lateral lobes connected by a narrow, median isthmus. Morphological and developmental anomalies of thyroid gland such as hypoplasia, ectopic thyroid, persistence of pyramidal lobe, thyroglossal cyst are common. Agenesis of thyroid gland with or without the involvement of isthmus is a rare congenital anomaly. The incidence has been reported to vary from 5% to 10%. The absence can be explained, as an anomaly of embryological development. It can be associated with other types of dysorganogenesis, such as the absence of a lobe or the presence of ectopic thyroid tissue. Agenesis of isthmus does not cause clinical symptoms by itself, and diagnosis is secondary due to existence of other thyroid pathology.
Aim: The aim of this study was to evaluate the incidence of agenesis of isthmus of thyroid gland and to discuss its embryological, genetic bases and clinical implications.
Materials and Methods:  The study was conducted on 30 adult human embalmed cadavers collected from Department of Anatomy, Sri Siddhartha Medical College, Tumkur, Karnataka, India by dissection method. The morphology of the thyroid gland was studied, and presence or absence of isthmus was noted. The length of the lobes and isthmus were noted. The specimens were photographed.
Results:  Three out of the 30 cadavers dissected showed agenesis of isthmus of thyroid.The respective lateral lobes were positioned independently on either side of trachea. The average length of the lobe of the thyroid gland was 5 cm on the right side and 4.5 cm on the left side. The average height of the isthmus was 1.75 cm. There were no significant variations in neurovascular relations. No tissue or structures similar to thyroid tissue were noted along its developmental route.

Conclusion: Agenesis of isthmus is an uncommon presentation that is frequently asymptomatic and detected incidentally when imaging for another condition. The absence may be due to an error in development or due to mutations of genes associated with thyroid gland. In clinical practice, when an image of the absence of isthmus is found, it is necessary to perform a differential diagnosis against other pathologies such as autonomous thyroid nodule, thyroiditis, ectopic thyroid tissue etc Knowledge of thyroid isthmus agenesis assumes surgical significance, as this has relevance in the resection of thyroid, tumours and tracheostomy.
KEY WORDS: Thyroid Agenesis, Ectopic Thyroid, Tracheostomy, PAX8 Gene, TITF2 Gene, Thyroiditis.


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Archana Belavadi Jagadish, Pradeep Prabhakar, Lakshmi Prabha Subhash R. A CADAVERIC STUDY OF AGENESIS OF ISTHMUS OF THYROID GLAND WITH EMBRYOLOGICAL, GENETIC BASES AND CLINICAL SIGNIFICANCE. Int J Anat Res 2016;4(2):2386-2391. DOI: 10.16965/ijar.2016.225




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