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There is a connection between carpal tunnel syndrome (CTS) and hypothyroidism (an underactive thyroid), but even in people with both conditions, it is not clear that hypothyroidism actually causes CTS. Studies show that CTS may develop in up to 10 percent of people with hypothyroidism and often symptoms of CTS will disappear when the thyroid disease is treated.
CTS is a common condition in which a large nerve (called the median nerve) is compressed or irritated in a narrow part of the wrist (called the carpal tunnel). Symptoms include numbness and tingling in the thumb, index and middle fingers and weakness or wasting of muscles in the thumb. Some people experience significant pain in the hand or fingers that may radiate into the forearm. In many cases, CTS develops for no identifiable reason, but pregnancy, certain occupations that stress the wrist, injuries and arthritis are among the most common causes.
Hypothyroidism is also common and may cause a number of symptoms including weight gain, fatigue, feeling unusually cold, constipation, dry skin, and hoarse voice. Many people with this condition feel depressed.
The reason for the association between hypothyroidism and CTS is not entirely clear, but it is thought that a buildup of fluid and connective tissue (the substance filling the spaces between cells) increases the pressure in the carpal tunnel, causing irritation of the median nerve.
Your question is a good one because the connection between these two common conditions is not widely appreciated, and knowing about it may improve evaluation and treatment. For instance, it is a good idea for people with newly diagnosed CTS to have thyroid function testing. If hypothyroidism is present in a person with CTS, treatment of the thyroid condition (with thyroid hormone replacement) can eliminate CTS as well as the other symptoms and complications of hypothyroidism; if not recognized, unnecessary carpal tunnel surgery and other symptoms and health problems may follow.
