Pyramidal lobe of thyroid
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The pyramidal lobe of thyroid (also known as Lalouette pyramid 5) is a normal anatomic variant representing a superior sliver of thyroid tissue arising from the thyroid isthmus. It is seen as a third thyroid lobe and is present in 10-30% of the population.
It represents a persistent remnant of the thyroglossal duct. It usually arises from the right or left side of the isthmus extending in a cranial direction; pyramidal lobes arising directly from the midline of the isthmus were rare in a large ultrasound study, accounting for only 2% of the cases 3.
It is not uncommon to see it on routine thyroid ultrasound, a study of 416 patients in 2014 found it in 21% 3.
All the pathologies that may be seen in the normal thyroid are also seen in the pyramidal lobe.
A band of fibrous tissue may be present extending superiorly from the pyramidal lobe to the hyoid bone, sometimes with a skeletal muscle component, termed the levator glandulae thyroideae muscle 4.
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- 3. Mortensen C, Lockyer H, Loveday E. The incidence and morphological features of pyramidal lobe on thyroid ultrasound. (2014) Ultrasound (Leeds, England). 22 (4): 192-8. doi:10.1177/1742271X14554677 - Pubmed
- 4. Chaudhary P, Singh Z, Khullar M, Arora K. Levator glandulae thyroideae, a fibromusculoglandular band with absence of pyramidal lobe and its innervation: a case report. (2013) Journal of clinical and diagnostic research : JCDR. 7 (7): 1421-4. doi:10.7860/JCDR/2013/6144.3186 - Pubmed
- 5. Germano A, Schmitt W, Carvalho MR, Marques RM. Normal ultrasound anatomy and common anatomical variants of the thyroid gland plus adjacent structures - A pictorial review. (2019) Clinical imaging. 58: 114-128. doi:10.1016/j.clinimag.2019.07.002 - Pubmed