When 鶹ý wrote that Democratic presidential candidate Hillary Clinton's physician, , had released additional health information about Clinton, one item received several comments: Bardack's use of the porcine product Armour Thyroid rather than levothyroxine (Synthroid) to treat Clinton's hypothyroidism.
"Armour Thyroid. One would think we could do better for our former First Lady," wrote one commenter.
"I am glad to hear she is taking Armour Thyroid rather than synthetic substitutes which contain only T4 and not T3. I always prescribed Armour for my patients because it is more natural, safer and more effective," wrote another.
Armour Thyroid is a thyroid tablet and "has a strong, characteristic odor," according to the drug's prescribing information. The tablets "provide 38 mcg levothyroxine (T4) and 9 mcg liothyronine (T3) per grain of thyroid."
Although thyroid hormone extracts have been used for centuries, the first reports of use in the English-speaking medical literature were in England in 1891, explained , an endocrinologist at Beth Israel Deaconness Medical Center in Boston and associate professor of medicine at Harvard Medical School. Initially the extract was derived from sheep and given in the form of an injection.
However, "it turned out it was difficult to make these preparations and keep them pure," so the injections were turned into tablets "and for probably the next 50-60 years, from the turn of the century to 1970, the standard hormone replacement therapy was thyroid hormone extract," made from either beef or pork thyroid, said Hennessey, who authored a .
Humans vs Animals
At that point, the pharmaceutical industry began noticing the difference in the hormonal makeup of humans and animals -- specifically the ratio between T4 and T3. In humans, that ratio is 14 to 1, compared with 4 to 1 in pigs and cows, he explained. So combinations of T4 and T3 hormones were brought on board in the early 1970s to try to better mimic what normally happened in humans.
But then researchers determined that people who were given thyroxine alone could convert it to T3, and when circulating levels of thyroid hormone were analyzed, "researchers were able to demonstrate that serum levels of thyroid hormone were very abnormal if patients were swallowing T3; they were also kind of abnormal if people were swallowing thyroid hormone extract -- T4 levels on the low side and T3 on the high side," said Hennessey.
"But when they were swallowing thyroxine alone, it looked like over the course of a day, thyroid hormone levels were in the expected range and indistinguishable for most part from those of us that don't have thyroid disease." So physicians began switching their patients away from thyroid extract and combination regimens to thyroxine alone.
There was some renewed interest in the late 1990s and early 2000s in adding T3 back, but the studies really didn't seem to support the idea that doing so had superior results. And in 2012, the American Thyroid Association and the American Association of Clinical Endocrinologists issued a as the treatment of choice, Hennessey explained.
Opinions Vary
Opinions on the use of Armour Thyroid differ among physicians. "Armour Thyroid is an antiquated product and has not been the standard of care for some time, as it is difficult to know the exact dose of thyroid hormone that the patient is taking," , a family physician in Brea, Calif., wrote in an email. "It is generally not recommended by endocrinologists."
"It has fallen out of favor and has been taken off of many drug formularies for this reason. There are better options available for treatment of hypothyroidism."
, of the University of Michigan in Ann Arbor, was more measured. "Endocrinologists prefer levothyroxine over Armour Thyroid because levothyroxine results in steadier levels of T3 in the blood, more closely mimics normal thyroid function, and makes it easier to interpret the results of thyroid blood tests," he wrote in an email.
"However, a very small fraction of patients seem to feel better when taking Armour Thyroid. The explanation for this is not known, but this is the main reason some patients take Armour Thyroid. In general, when used in appropriate doses, either levothyroxine or Armour Thyroid should result in a good health outcome."
"Some physicians use it in most patients, others in patients who do not do well, and others, like me, very rarely consider using Armour Thyroid," , of the University of Colorado Denver, wrote in an email. "The people who use and support it claim that some patients feel better on thyroid extracts like Armour than levothyroxine therapy alone, and there is some weak short-term evidence to support that."
"My feeling is that is a physician is prescribing Armour Thyroid, it should be given twice daily instead of once daily like we do with levothyroxine," he continued. "This is because of the shorter half-life of T3 and what we know from studies with oral T3 (Cytomel) therapy. We need to make sure the serum [thyroid-stimulating hormone] is kept in the reference range as we do for any patient with hypothyroidism on any thyroid hormone therapy. I would also be a bit worried about Mrs. Clinton being on Armour thyroid, since older patients are at increased risk for heart rhythm problems if too much thyroid hormone is given."
Some More Favorable
, a retired family physician who specialized in treating mental illness through nutrition and who practiced in Kendall Park, N.J., has a more favorable opinion of Armour Thyroid. "I prescribed Armour Thyroid because it is a more natural and complete substance, containing both T4 and T3, as well as the little known mono and di-iodothyronine, the entire range of thyroid hormones," she wrote in an email. "The conventional approach is to use levothyroxine, which is only T4, because doctors are taught in medical school that desiccated thyroid is unstable and unreliable in terms of dosage and that synthetic is better."
However, she said, "I saw ... patients who were on Synthroid and not feeling any better, who improved when switched to Armour. I usually ordered Free T4, Free T3, TSH, and anti-thyroid antibodies to check for Hashimoto's thyroiditis. If the Free T3 level is lower than the Free T4 level, it is useless to treat with Synthroid because the patient is unable to convert enough T4 into T3, perhaps because of a deficiency of selenium, omega-3 fatty acids or zinc."
Hennessey noted that the big concern with Armour Thyroid is that the patient might get too much T3, and added that Clinton may have been started on thyroid replacement therapy in the 60s or early 70s, when Armour Thyroid was still the treatment of choice. If it works well for her -- if she's feeling well, and her tests show that her T3 levels aren't too high, "then if that's what floats her boat, leave it alone."