By Dr. Caroline Stratz

Q: I have been feeling very tired lately. A friend mentioned I might have a thyroid disorder. What can you tell me about it?

A: You may be one of 13 million Americans with an underactive thyroid gland, also known as hypothyroidism. Women are two to three times more likely than men to develop this condition, and the risk rises with age. Recent changes in how hypothyroidism is defined may lead to even more people being diagnosed.

The thyroid gland is found right below the Adam’s apple. This small but important gland (it’s only 2 inches wide) manufactures hormones that control your metabolism. The most important thyroid hormone is thyroxine (T4). If the thyroid doesn’t make enough T4, hypothyroidism will result.

The thyroid can fail for a number of reasons, including certain medications and radiation treatments to the head and neck. Thyroid problems are also often associated with pregnancy and childbirth, although the condition is usually not permanent. Most cases of hypothyroidism in this country are due to Hashimoto’s disease, which usually affects women in their 30s and 40s. In this case, the immune cells mistakenly attack the thyroid, damaging the gland and the production of hormones over time. Weight gain, fatigue and depression are some of the most common symptoms associated with hypothyroidism. You may also feel chilly, notice a decrease in your libido or develop dry hair and skin.

Many of these symptoms are very common in the general population and don’t necessarily indicate a thyroid disorder, but your doctor can tell you for sure. Your doctor should take a complete medical history as well as a relevant family history, as the disorder can run in families.

A simple blood test measuring your thyroid-stimulating hormone (TSH) can answer the question quite easily. TSH is produced by the pituitary gland (in the brain) and will rise considerably if your thyroid isn’t doing its job.

The reverse is also true. The TSH will be very low if the thyroid is producing too much hormone, a condition known as hyperthyroidism.

Until recently, it was thought that a TSH value between 0.5 and 5 micrograms was considered normal. A measurement over 5 indicated an underactive thyroid. However, newer guidelines advise the upper limit of normal to be at 3, which may mean many more people coupld be diagnosed with hypothyroidism. It is recommended that all adults have their thyroid function tested every five years.

Treating hypothyroidism is relatively straightforward. The deficient hormone is replaced with a synthetic version known as levothyroxine. Patients usually begin with a small dose, which is adjusted as necessary.

Once the correct dose is found, the TSH levels return to normal and symptoms most often disappear. Ask your doctor about your health and lifestyle with the goal of preventing health problems before they occur.

Dr. Caroline K. Stratz is an internist in private practice near El Camino Hospital. Her practice focuses on personalized health care that emphasizes comprehensive medical histories and examinations, health risk and lifestyle appraisals, and making herself accessible to her patients. For more information, call 988-9975.