November 15, 2004

Question: I have been on Synthroid since 1997. The whole time, I've had extremely itchy blisters, mostly on my lower legs. I can’t stand the itching, so I pop the blisters. This leaves an open sore, and twice, I’ve been hospitalized due to bad skin infections. Are these eruptions part of my hypothyroidism symptoms?

Dr. Lowe: I am sorry you’ve been troubled by the blisters on your legs. Blisters aren’t a common sign of hypothyroidism. (We list the most common signs of hypothyroidism on drlowe.com.) Nonetheless, I know of two reports in which researchers described blisters as a sign of hypothyroidism.

Researchers reported the case of a 73-year-old-Japanese woman who was hypothyroid but not taking thyroid hormone.[1] Slight abrasions caused blisters to form on her fingertips, toes, and the insteps of her feet. After she began taking thyroid hormone, the abrasion-induced blisters markedly decreased. The researchers wrote that the patient’s blisters were related to her low thyroid hormone level.

Other researchers reported the case of a 70-year-old man whose hypothyroidism was untreated. He had blisters on the outsides of his legs.[2] The researchers described the blisters as "pretibial epidermolysis bullosa." The term "pretibial" refers to the skin over and beside the tibia. The tibia is the bone in the front of the leg that extends from the knee to the ankle. The term "epidermolysis bullosa" simply means that the skin beside the tibia in the man responded to slight mechanical trauma by forming large blisters and erosions.

After the man began taking thyroid hormone, the number of blisters decreased; finally, they disappeared altogether. At a followup exam 12 months later, the man reported that no more blisters had formed.

The researchers conjectured that the blisters had formed because the involved skin was weak, and it was easily irritated by mild friction. They wrote that the lack of recurrences of the blisters meant that they were a feature of the man’s hypothyroidism. They concluded, "Our case confirms the reality of hypothyroidism pretibial epidermolysis bullosa," and they advised doctors to test patients with skin blisters for hypothyroidism. They described another case report similar to theirs, but I haven’t been able to locate it.

It is possible, then, that the blisters and eruptions on your legs are a sign of your hypothyroidism. If so, Synthroid appears to be an ineffective treatment for you, as it is for many other patients. Switching from T4-replacement with Synthroid to a T4/T3 product—with your dosage adjusted by your clinical response and not your TSH level—may permanently eliminate your blisters. I certainly hope so.

References

[1] Mochizuki, T., Tanaka, S., and Watanabe, S.: A case of hypothyroidism with bulla formation. Dermatologica, 1984;169(3):146-149.

[2] Le Brun, V., Boulinguez, S., Bouyssou-Gauthier, M.L., et al.: Pretibial epidermolysis bullosa and hypothyroidism. Ann Dermatol Venereol., 2000, 127(2):184-187.