Hashimoto’s thryoiditis not rare

Dear Dr. Roach: Please explain Hashimoto’s disease. I have heard it is rare, but two colleagues have recently been diagnosed. We all work in a very high-stress field.

Answer: Hashimoto’s thyroiditis is not at all a rare disease, occurring in up to 10% of the population and in women much more frequently than men.

Although people can be diagnosed at a young age, it is more common at older ages. It is caused by an autoimmune reaction to different parts of the thyroid, with thyroglobulin and thyroid peroxidase antibodies commonly found and TSH receptor antibodies found on occasion.

Hashimoto’s thyroiditis most commonly causes low thyroid levels, although there may be a period of time early in the disease where the thyroid levels are high.

Not everybody with antibodies will develop low thyroid levels. The thyroid is sometimes enlarged, but a careful exam will usually show that the gland is firm, representing that immune cells have infiltrated the gland.

Treatment of Hashimoto’s thyroiditis involves replacing the thyroid hormone that the gland can no longer make.

The dose depends on body size to a certain extent, but needs to be adjusted based on lab results. Most people are treated with levothyroxine, also called T4, which is the primary hormone made by the thyroid.

T4 is converted to T3 (also called triiodothyronine, the active form of the hormone) in various tissues outside the thyroid.

T3 only stays in the body for a short while before it is destroyed, so a once-daily treatment with T4, which lasts longer, allows the body to convert T4 to T3.

Most people do very well with T4 treatment. A minority of people cannot efficiently make the active T3 from T4, in which case combination treatment can be considered. Unfortunately, T3 must be dosed twice daily.

It is thought that stress hormones may play a role in this, since stress does seem to increase the risk of developing an autoimmune thyroid disease like Hashimoto’s thyroiditis.