Agenesis of thyroid gland

• Thyroid agenesis is the complete absence of the thyroid gland from birth.

• Congenital hypothyroidism is a condition that results from inadequate thyroid hormone production from birth, the worldwide incidence 1:3000 to 1:4000. The condition can be categorized in terms of etiology as thyroid agenesis (22–42%), ectopic thyroid gland (35–42%), or gland in situ abnormalities (24–36%)

Picture 1:

The thyroid gland not seen in normal position and no ectopic thyroid tissue, small anechoic hypo-vascular t cystic nodule seen in Rt lobe bed.

• Thyroid hemi-agenesis is defined as the lack of development of one thyroid lobe or one thyroid lobe and thyroid isthmus.

• Hemi-agenesis of thyroid gland is a rare condition, only 300 case had been reposted till 2010 3 and been first reported by Handsfield-Jones in 1866.

• In the general population the prevalence estimated from screening ultrasound studies is approximately 0.06% (ranging 0.05% to 0.2%), left thyroid lobe being more common.

• More common in female with 3;1 female to male ratio.

• The higher frequency of hemi-agenesis occur in left lobe in 80% of the reported cases and associated with isthmus agenesis in 50% of the cases.

Picture 2:

37 y old female , mildly enlarged Rt lobe of thyroid gland , congenital agenesis of the isthmus and Lt lobe, Small thin wall anechoic hypo-vascular cystic nodule of 3*3*2mm seen in Lt lobe bed.

Picture 3:

Female 38y old, normal Rt lobe and isthmus with agenesis of Lt lobe

Picture 4:

Agenesis of the Rt lobe and isthmus, normal Lt lobe size