Your Thyroid: What You Need to Know

It’s shaped like a butterfly and makes hormones that regulate how fast your heart beats and how many calories your body burns. It’s your thyroid, and it can get out of whack, particularly if you’re a woman and as you get older.

Thyroid disorders include thyroid cancer, hypothyroidism (underactive thyroid), hyperthyroidism (overactive thyroid), and autoimmune thyroid diseases such as Hashimoto’s disease and Graves’ disease. According to endocrinologist Jack Merendino, MD, doctors are challenging some long-held beliefs about the diagnosis and treatment of thyroid disorders.
Hypothyroidism: Which Hormones Do I Need?
Hypothyroidism means that your thyroid isn’t producing enough of the hormones it’s supposed to make. Symptoms can include fatigue and weight gain, which nobody wants. So how does it happen and what can you do about it?
The thyroid manufactures and releases two hormones, colloquially known as T4 and T3. These hormones influence all kinds of important body functions, including how your body uses and stores energy, your brain function, weight and even breathing. When your thyroid doesn’t produce enough of these hormones (often due to an autoimmune disease, medication or thyroid surgery) you have hypothyroidism, and you’re going to need synthetic thyroid hormone.
T3 is more important biologically and more potent, “but the conventional treatment [for hypothyroidism] is [synthetic] T4,” according to Dr. Merendino. “The big question surrounds whether conversion of ingested T4 into T3 is adequate. Certain patients feel better when treated with both, but in the majority, that’s not what’s done.”
People have different genetic variants of the enzyme that converts T4 into T3. “One thought that’s as yet unproven is people who inherit the variant that’s less active might respond more favorably to combination [T4 and T3] therapy,” he says.
According to Merendino, the synthetic form of T4 is easier to manufacture and store. Synthetic T3 “has a shorter shelf life,” he says. T3 also fluctuates more in the bloodstream when taken in synthetic form. “Where T4 gives you a steady level of the hormone over 24 hours, if you take T3 the levels vary substantially over 24 hours,” says Merendino.
With home genetic testing becoming more and more common, Merendino says patients can easily find out which variant of the conversion enzyme (called deiodinase)they have. “That information is out there and I think people who are doing their own testing will come in [to doctors’ offices] more,” says Merendino. If you’re not feeling better after giving T4 therapy an honest attempt, it might be time to consider combination therapy.
Autoimmune Disease: The Surprising Link Between Your Thyroid and This Condition
“Autoimmunity is a major category of disease, and thyroid disease is the most common autoimmune disease,” says Merendino. “Autoimmune thyroid disease is overwhelmingly more common in women, by four- or fivefold.”
What’s more, if you have autoimmune thyroid disease, your chances of having other autoimmune diseases are increased. The autoimmune disease that’s getting a lot of press lately is celiac disease, the chance of which is increased by anywhere from 2% to 5% for people with an autoimmune thyroid condition such as Hashimoto’s disease, which results in hypothyroidism, or Graves’ disease, which causes overactive thyroid.
Celiac disease may make all the headlines, but Merendino says not to panic because there is a lot of interest around something that is more rare than you might think. “Many people think, ‘If I have thyroid disease then I have Celiac disease,’” he says. “But if you realize that about 1% of the population has celiac disease, that’s about 1 in 300 people with an autoimmune thyroid disease also have Celiac disease.”
Thyroid Cancer: Advances in Diagnosis
A 2006 study showed that incidences of thyroid cancer increased by 2.5 times between 1973 and 2002, and rates continue to increase. But the question is, are more people getting thyroid cancer, or are doctors getting better at finding it? Tellingly, while the number of new cases has gone up since 2002, the number of deaths per year hasn’t. 
“Thyroid cancer is, by and large, not an aggressive cancer,” says Merendino. “Most patients don’t notice it. But we’re finding it more and more because it used to have to be big enough to feel.”
For about three decades, doctors have used small needles to extract cells and look at them under a microscope. But now, genetic testing is “supplementing and may come to supplant looking at cells under a microscope,” according to Merendino. That’s important, he says, because thyroid cancer cells don’t look much different than regular thyroid cells. Merendino says that if a nodule is bigger than a centimeter, it should probably come out.
“The majority of people with nodules in my office have detected them because they’ve gotten a CAT scan in their neck or a carotid ultrasound,” he says. “It’s showing more and more frequently. Over the last 40 or 50 years, the apparent incidence has risen dramatically but the death rate has hardly changed.”