Birefringent crystals of calcium oxalate have been previously identified in the colloid of human thyroid glands. We found such crystals in 19/20 adult thyroids at autopsy, in 4/ 20 infants at autopsy, and, using frozen sections, in 19/20 thyroids partially or totally removed at surgery. These crystals were soluble in hydrochloric acid, insoluble in acetic acid, and contained only calcium by energy dispersive X-ray microanalysis, confirming their calcium oxalate character. Similar crystals were found in equine and ovine thyroids.
Hackett, Raymond L. and Khan, Saeed R.
"Presence of Calcium Oxalate Crystals in the Mammalian Thyroid Gland,"
Scanning Microscopy: Vol. 2
, Article 21.
Available at: https://digitalcommons.usu.edu/microscopy/vol2/iss1/21