Thyroid hemiagenesis: a rare finding

Ultrasound of the Normal Thyroid with Technical Pearls and Pitfalls

Ultrasound is the best imaging modality for comprehensive evaluation of the thyroid. The thyroid is best imaged using a high-frequency linear probe with the patient in a supine position with the neck hyperextended. Normal thyroid is homogeneous in appearance without defining anatomic landmarks within the gland. A few anatomic variants can occur, and it is important for the sonographer and radiologist to be aware of these variants, to avoid misidentifying them as a pathology. This article provides a comprehensive review of ultrasound of the normal thyroid gland, including technique, normal anatomy, anatomic variants, imaging appearance, and technical pearls and pitfalls.

Thyroid hemiagenesis associated with multinodular goiter and Hashimoto's thyroiditis

Thyroid hemiagenesis is a rare congenital abnormality in which one of the thyroid lobes is not developed. It can be associated with various thyroid diseases, such as Grave's disease, nodular goiter and thyroid neoplasm, rarely with hyperparathyroidism. We report a case of a 50-year old woman with left thyroid lobe agenesis diagnosed by ultrasonography and scintigraphy. Right thyroidectomy was performed and the histopathological examination showed diffuse hyperplasia, multinodular goiter and Hashimoto's thyroiditis. To our knowledge, this is the first description of multinodular goiter and Hashimoto's thyroiditis in a patient with thyroid hemiagenesis.

Mechanisms of thyroid development and dysgenesis: an analysis based on developmental stages and concurrent embryonic anatomy

Thyroid dysgenesis is the most common cause of congenital hypothyroidism that affects 1 in 3000 newborns. Although a number of pathogenetic mutations in thyroid developmental genes have been identified, the molecular mechanism of disease is unknown in most cases. This chapter summarizes the current knowledge of normal thyroid development and puts the different developmental stages in perspective, from the time of foregut endoderm patterning to the final shaping of pharyngeal anatomy, for understanding how specific malformations may arise. At the cellular level, we will also discuss fate determination of follicular and C-cell progenitors and their subsequent embryonic growth, migration, and differentiation as the different thyroid primordia evolve and merge to establish the final size and shape of the gland.