To the Editor:—
The signs of thyrotoxicosis have been memorized by medical students for decades; however, changes in skin pigmentation seem to be frequently overlooked. In our experience, alterations in pigmentation have been a useful and interesting physical finding.
Increases in pigmentation are often seen in exophthalmic goiter (Graves' disease) and may be either diffuse or chloasmal in nature. These skin changes can be seen in either exposed or unexposed areas but are rarely seen on the buccal mucosa, nipples, or genitals.
The cause of the pigmentary changes is still speculative; however, it is known that the pigment is melanin. Tyrosine is an amino acid common to both melanin and thyroxine; and it is well established that patients with thyrotoxicosis have tyrosine intolerance with elevated serum tyrosine levels.1
Many theories have been advanced to explain the phenomenon of hyperpigmentation such as elevated levels of adrenocorticotropic hormone (ACTH) or tyrosine,
. . . [Full Text PDF of this Article]
