Hypothyroidism (underactive thyroid) was discussed in column a few weeks ago. To review, the thyroid is a gland located in the front of the neck that regulates our metabolism. It produces T4 (4 iodine atoms), which after entering the bloodstream is converted to T3 (3 iodine atoms). Production of T4 is regulated by TSH (thyroid stimulating hormone]), produced by the hypothalamus located in the base of the brain.

Hyperthyroidism is less common than hypothyroidism. Symptoms include sweating; weight loss (rarely weight gain); anxiety; heart irregularities including palpitations and atrial fibrillation; rapid pule rate; loose stools; heat intolerance; fatigue; menstrual irregularity; osteoporosis; and tremor. Following are the common causes of hyperthyroidism:

• Graves’ disease, which is more common in women, is the most common cause of hyperthyroidism. It is an autoimmune disease, where a rogue immune system attacks the thyroid gland in a way that causes it to produce too much hormone.

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• Sometimes one or more tumors called “nodules” produce excessive thyroid hormone. These are usually although not always benign.

• Too high a dose of thyroid replacement hormone, given to treat hypothyroidism, is another cause.

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• too much daily intake of iodine

Lab findings in hyperthyroidism include low TSH (the pituitary stops stimulating the thyroid gland when it’s producing too much thyroid hormone), high T4 and/or T3. An ultrasound scan of the thyroid helps determine the cause of hyperthyroidism, since it picks up abnormalities such as nodules.

Depending on the cause of hyperthyroidism, treatment options include the following: surgery to remove part or all of the gland; radioactive iodine, which destroys part or all of the gland, often resulting in hypothyroidism — which is easily treated by daily thyroid replacement pills (T4—levothyroxine); and medications, which can be associated with serious side effects. While awaiting results from one of these definitive treatments, a beta blocker called propranolol controls symptoms of hyperthyroidism such as rapid, pounding pulse.

Dr. Neal Barnard’s book “Your Body in Balance” points out that since Graves’ disease is a common cause of hyperthyroidism, “immune-friendly foods” are helpful prevention and treatment. People who eat animal products have higher levels of thyroid antibodies compared with people on a plant-based, whole food diet. In one study, vegans “were 52 percent less likely to have hyperthyroidism, compared with meat-eaters.”

Greg Feinsinger, M.D. is a retired family physician who has a nonprofit: Prevention and Treatment of Disease Through Nutrition. He is available by appointment for free consultations (379-5718).