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by Mary Shomon

It may be legal, and it may be a staple ingredient in many of our most popular beverages, but caffeine has a place right along with other drugs in most major drug databases such as Johns Hopkins' Intellihealth.

Caffeine is a stimulant, and has an effect on your central nervous system, your digestive tract, and your metabolism. Also according to Intellihealth, "in high doses, caffeine can cause rapid heartbeat, irritability, insomnia and anxiety in some people."

Caffeine has at times been associated with various illnesses, such as heart disease, infertility miscarriage, and fibrocystic breasts. While there's strong evidence that caffeine has major effects on both body and mind, however, there's a lack of clear scientific evidence to prove the cause-and-effect nature of some of the relationships with diseases.

So when it comes to thyroid disease, there's a question as to whether caffeine is a drug of particular concern to many thyroid patients. Anecdotal information from a number of site visitors -- and my own experience as well -- points to the fact that caffeine can potentially be a factor that worsens symptoms.

One regular poster at a Thyroid Bulletin Board had written about the symptoms she assumed were her thyroid problem:

"The symptoms I was experiencing were not thyroid related, just as the docs said, but the result of excessive coffee consumption. I only found this out after stopping all coffee consumption about six weeks ago. Some of these symptoms are very similar to thyroid disease symptoms and since I did have thyroid disease that is the area I explored. A very easy mistake to make especially since caffeine containing products are promoted as innocuous beverages...Ever since stopping a 25 yr. ten cup minimum per day coffee habit all my adverse symptoms, and there were many, have stopped. Today I feel perfectly normal."

As she found out, some of the symptoms of too much caffeine can mirror undertreated or untreated hyperthyroidism and hypothyroidism. Symptoms include: restlessness, nervousness, excitement, insomnia, flushed face, frequent urination, stomach disturbance, muscle twitching, rambling flow of thought and speech, fast heartbeat or cardiac arrhythmia, and more. And caffeine, like many stimulants, can be very problematic for someone with untreated hyperthyroidism, or who is in the process of receiving treatment for hyperthyroidism.

More information on caffeine symptoms is available in the Caffeine FAQ.

In addition to similarity of some symptoms, there is a suspected hormonal relationship between the thyroid and caffeine. According to researchers, "Caffeine has been shown to markedly alter...thyroid stimulating hormone (TSH), and thyroid hormones in animal studies. Similar studies in the human are lacking." (Dev Pharmacol Ther 1987;10(2):73-80) Other researchers found that "chronic caffeine therapy," constituted by high levels of caffeine use over time, "stimulated both T4 and TSH; however, TRH-stimulated TSH release was decreased, suggesting that chronic therapy may blunt pituitary TSH response." (Pediatr Res 1983 Jul;17(7):592-595).

Recognizing that caffeine may impact the thyroid's ability to function, therefore, is enough reason to consider cutting out or cutting down on caffeine.

Let's look at a few other things we do know about caffeine and thyroid-related symptoms.

We now know know that hypothyroidism is a major contributing cause to many cases of carpal tunnel syndrome (CTS). And for those people with hypothyroidism who suffer from this debilitating CTS wrist/arm/finger pain, it's been found that caffeine is a also a possible culprit in aggravating carpal tunnel syndrome.

Another reader, Ron, wrote regarding his carpal tunnel syndrome and caffeine. He writes:

"I read your article on hypothyroidism and CTS. I have CTS and my father had CTS too. I don't know if there is a genetic connection or not. But what I did discover is that caffeine aggravates CTS, and eliminating it from my diet reduced the symptoms significantly. After I retired, we always had a pot of coffee available. I sipped coffee throughout the day. I had difficulty holding the newspaper for any length of time to read it. At night I would wake up with hands numb and excruciating pain up to my elbows. While on a trip I didn't have any caffeine for 3 or 4 days. My CTS improved dramatically; so I stayed off caffeine. The longer I was off the stuff the better my hands became. Now I have one or two cups of tea a day. My hands are not as good as when I totally refrain from caffeine but is tolerable. It takes 3 or 4 days to get over the caffeine withdrawal; then the CTS improves with time up to a point where under normal conditions I didn't know I had the problem. More people should try this solution to CTS."

So if carpal tunnel, or other nerve and swelling-related problems are plaguing you, you might want to consider cutting out the caffeine.

Here is a chart of the caffeine content of your favorite beverages:

Coffee, brewed	40 to 180 milligrams (mg) per cup.
Coffee, instant	30 to 120 mg per cup.
Coffee, decaffeinated	3 to 5 mg per cup.
Tea, brewed American	20 to 90 mg per cup.
Tea, brewed imported	25 to 110 mg per cup.
Tea, instant	28 mg per cup.
Tea, canned iced	22 to 36 mg per 12 ounces.
Cola and other soft drinks, caffeine-containing	36 to 90 mg per 12 ounces. (i.e., Mountain Dew, 55.0; Coca-Cola, 45.6; Dr. Pepper, 39.6; and Diet Pepsi, 35.4)
Cola and other soft drinks, decaffeinated	0 mg per 12 ounces.
Cocoa	4 mg per cup.
Chocolate, milk	3 to 6 mg per ounce.
Chocolate, bittersweet	25 mg per ounce.

It's known that caffeine causes urinary excretion of calcium. The Journal of the American Medical Association (JAMA) (JAMA, 26 Jan. 1994, p. 280-3) found that "There was a significant association between (drinking more) caffeinated coffee and decreasing bone mineral density at both the hip and the spine, independent of age, obesity, years since menopause, and the use of tobacco, estrogen, alcohol, thiazides, and calcium supplements [in women]. The decreased bone density could be offset for women who drank milk on a daily basis."

So, from the thyroid disease perspective, many of us are aware that hyperthyroid TSH levels, or overdosage of thyroid hormone into hyperthyroid levels can sap the body of calcium, and increase the risk of osteoporosis. There is also controversy over whether or not treatment with thyroid hormone that puts patients' TSH in the low-normal range can increase the risk of osteoporosis as well. Thyroxine and calcitonin are secreted by the thyroid gland, so a thyroid gland that has either been surgically removed, or is not fully functional, can inhibit bone mineral metabolisim and negatively affect bone mineral density. (Chung Hua Chung 1996 Jul;18(4):308-309 ).

But even with the various controveries, it's clear that most women with thyroid disease should already be paying special attention to fulfilling their calcium requirements in order to avoid the potential of an increased risk of osteoporosis.

Groundbreaking research reported in the American Journal of Obstetrics and Gynecology showed that calcium may ease premenstrual syndrome (PMS) symptoms. The study found that women who take approximately 1,200 milligrams of calcium each day for approximately three months can reduce many symptoms of PMS by more than half. Doctors claim that that calcium works on all groups of symptoms, including headaches, food cravings, mood swings, pain, depression symptoms, and bloating. It is difficult to obtain 1200 mg of calcium simply from diet, so doctors were recommending a serving of a low-fat milk product, plus two or three tablets of a chewable calcium supplement, such as Tums. Lead investigator, endocrinologist Susan Thys-Jacobs, believe that there may even be a link between PMS and osteoporosis. Calcium depletion may interact with the female hormones estrogen and progesterone at certain stages of the menstrual cycle, leading to the physical and emotional discomfort of PMS. Says Thys-Jacobs, "We think women are being given a signal by the body that they are not taking in enough calcium.''

So now that calcium is suspected to affect hormonal balances in the body, it's interesting to speculate on whether there could be a relationship between calcium deficiency and the worsening of "thyroid" symptoms during the PMS phases of a woman's cycle.

"We think women are being given a signal by the body that they are not taking in enough calcium.''