The thyroid gland may have a black color due to a number of causes.
Drugs or chemicals:
(1) minocycline
(2) doxycycline
(3) possibly indocyanine green
Non-drug causes:
(1) hemochromatosis
(2) cystic fibrosis
(3) ochronosis
(4) hemorrhage
There appears to be an increased incidence of adenomas or papillary carcinomas associated with black thyroids
