Sunday, June 24, 2012
Take This With A Grain of Salt...
Iodine is not something Americans often discuss, but maybe they should more often.
Iodine is an essential trace element needed for humans to sustain life because of its main role is as a constituent of the main thyroid hormones, thyroxine (T4) and triiodothyroxine (T3). The thyroid gland needs no more than 70 micrograms per day of iodine to synthesize the requisite amounts of T4 and T3, but higher amounts (~150 micrograms per day) are needed for optimal function of a number of body systems, including milk-producing breasts, the lining of the stomach, the salivary glands and lining of the mouth, your thymus that produces you’re the key cells of the immune system, your skin, etc.
Worldwide, iodine deficiencies are common and can cause brain development issues. That is why here in the U.S., even though seafood is a good source of iodine, the government requires that our table salt be iodized (iodine is added) so the American public can maintain healthy levels of this essential element.
That’s great except there is one problem. Just like with the warnings to avoid sun exposure to avoid skin cancer has increased Vitamin D deficiencies, warnings to avoid salt may be causing iodine deficiencies. The problem is that very few doctors these days test for iodine deficiencies. I did the other day for the first time.
Let me tell you why I ordered this rather uncommon test. A patient came to me complaining of fatigue. As part of the work-up for fatigue, I did what are called thyroid function tests (TFTs). These tests included measuring her T4, T3 and Thyroid Stimulating Hormone (TSH) levels. The tests came back slightly abnormal and as a next step, I ordered a test for thyroid antibodies, which if positive would further indicate thyroid disease. They also came back slightly positive. I then ordered a thyroid ultrasound scan to see what was going on with this patient’s thyroid and it came back negative. I was confused as there were indications of thyroid disease, but the results were inconclusive. I decided it was best to refer the patient to an endocrinologist, the specialty doctor with expertise in endocrine diseases such as thyroid disease.
However, before the patient left, I decided to test one more thing—her iodine level. I did so because I remembered that the patient had previously told me that due to her elevated blood pressure she had completely refrained from adding any salt to her diet for a number of years. She also told me she had distaste for seafood. I wondered if the combination of her refraining from salt and almost never eating seafood had prevented her from getting sufficient iodine in her diet. The iodine test is uncommon and the results take five days before they are available. In the meantime, the patient had booked visits with two different endocrinologists, one who told her to take thyroid medicine (synthroid) for her thyroid disease and another who told her it was unnecessary because her thyroid was fine (no wonder I was unsure).
Meanwhile, the iodine test came back and guess what--that’s right, she had an iodine deficiency. I immediately researched other natural sources for iodine beyond seafood and iodized salt, and found out that there were not many good sources (milk products and egg yolks are a source, but I don’t generally recommend consumption of them for other reasons). Cranberries are another source, but not a great one.
So, given my unease with starting her on a iodine pill that can have some nasty side-effects, I suggested that she should instead add a teaspoon of iodized salt to her daily diet to correct the deficiency. I will obviously need to watch her blood pressure due to the added salt, but I hope this will correct her iodine deficiency and return her thyroid hormones to completely normal levels.
It's often said that when doctors hear hoof-beats, they should think of horses not zebras. In the case of abnormal thyroid tests and fatigue, checking iodine levels may actually turn out to be a horse.