What is considered a dangerously high TSH level

When I first suspected I was suffering from hypothyroidism, I did what any anxious, Internet-connected person would do and Googled "dysfunctional thyroid symptoms," and, in another tab, "hypothyroid thinning hair??" for good measure.

What came up sounded like someone describing me for an intimately detailed police sketch:

• increased fatigue
• heightened sensitivity to cold
• unexplained weight gain
• dry skin
• muscle weakness
• a pale, puffy face ("Finally, a medical explanation for this," I thought.)

This, combined with the fact that a close family member had recently been diagnosed with a thyroid disorder, sent me scurrying to the nearest endocrinologist's office. They took a blood test, and two weeks later the results came back. Sure enough, the doctor said solemnly, I had hypothyroidism, which meant my thyroid was under-active. She would be starting me on thyroid medication. She couldn't know for sure, but I might have to take drugs for the rest of my life.

I took the news well. This was, after all, exactly what I was hoping for—a pill that would act like kind of a Photoshop for real life, making me skinnier, more energetic, less puffy, and more moisturized practically overnight.

Just to be sure, though, I asked to see my blood test results. The document said I tested positive for Hashimoto's thyroiditis, a condition in which the immune system attacks the thyroid. (Somehow knowing I have a disease named after someone made it seem worse.)

At the same time, the blood test showed I had normal levels of the thyroid hormones T3 and T4, which play a critical role in regulating metabolism.

The doctor said my levels of TSH, the thyroid stimulating hormone that tells the thyroid to make T3 and T4, were too high, however. A high TSH is the marker that most endocrinologists use to diagnose hypothyroidism. It means the pituitary gland is telling the thyroid, "Go, go! Work harder!" And the thyroid is saying, "Chilll man, I'm sooo sleepy." Conversely, too little TSH means hyperthyroidism, or an over-active thyroid.

I studied my blood-work printout. My TSH levels were 3.5, which was, according to the lab, within the normal range of 0.35 to 5.5.

“This says the TSH is normal,” I said.

My doctor begged to differ.

"If you were pregnant or trying to get pregnant, we'd medicate you at 3.5," she said.

"But I'm not trying to get pregnant," I said.

"Well, a family doctor might not treat you for a 3.5, but an endocrinologist would. And that's what we're recommending," she said firmly. I was to call her, she added, if the meds gave me tremors or if my hair started falling out.

I stammered, saying I didn't really understand. I wasn't sure I wanted to take a pill for the rest of my life to fix something that wasn't technically broken. I mean, what if the side effects were worse than being slightly tired and puffy all the time?

“I don’t know if I’m ready for this!” I blurted, then realized I sounded like some sort of medicine-fearing anti-vaxer.

"Well, you don't have to take it," she said. "But it's perfectly safe."

She finally convinced me to take the prescription with me and think about whether I wanted to actually start on the drug.

"You know, you're low on Vitamin D, too," she added as I walked out the door. "You should really take a supplement. And don’t worry, it's all natural."

Little did I know that I had stumbled into one of the hottest controversies in endocrinology, one that touches on one of the most common diseases in the U.S. Twelve percent of Americans will develop some sort of thyroid disorder within their lifetimes, and levothyroxine, the drug used to treat hypothyroidism, is by some measures the second-most-frequently prescribed drug in the country. For some reason, thyroid disorders are exponentially more common in women than men. Hashimoto’s is hypothyroidism’s most common cause.

Many people—possibly up to 2 million—who have a thyroid disorder haven't been diagnosed. Some might lack access to or money for doctors, but for many, it’s just that the symptoms of hypothyroidism are so vague. Who doesn't feel tired, fat, and depressed sometimes?

"The symptoms of hypothyroidism are diverse and they mimic the symptoms of everyday life," said Scott Isaacs, the medical director at the Atlanta Endocrine Associates in Georgia. "They could be the thyroid, but they could be something else."

It's the TSH levels that are the source of all the squabble among doctors. Most doctors agree that any TSH above 10, especially when combined with an abnormal T3 or T4 reading, should be treated. Many labs, like mine, consider a TSH reading above five or so to be abnormal.

However, some studies have found that only 5 percent of people have a TSH above 2.5 (though others say it's more like 15 percent). That is to say, being above 2.5 is statistically abnormal. And abnormalities are, by and large, how medicine decides what a disease is.

People like me, whose level falls between 2.5 and 4.5, have a higher risk of developing full-blown hypothyroidism over time. That suggests, to some doctors, that the upper TSH limit should actually be lower—like four, or maybe even 2.5, as my endocrinologist said. The problem is, a 10th of Americans have a TSH level between 2.5 and 4.5, by some estimates. It's an awfully big step to suggest that an additional 30 million-some people belong on a medication for a condition they might never have heard of.

In 2004, a group of thyroid experts came together to figure out whether they should tweak the TSH range that should be considered normal. They concluded, essentially, that there's no compelling evidence to treat people whose TSH is below 10.

This prompted widespread consternation among patients and some doctors. Hypothyroidism feels crappy; some patients with readings of six or seven might be begging to be put on medication.

"What's normal for me may not be normal for you," said one prominent thyroid activist, Mary Shomon, to the New York Times in the wake of the 2004 findings. "We're patients, not lab values."

Last month, researchers from Oregon Health and Science University performed another meta-analysis. In 10 years, they wondered, have any new thyroid studies come out and shown that there's a benefit to treating people with so-called “subclinical” hypothyroidism?

Their findings, published last month in the Annals of Internal Medicine, confirmed the 2004 panel's conclusion. If a person has a TSH reading between four and 10, the authors found, there's no evidence that taking medication improves their quality of life or cognitive functioning. These individuals didn't lose weight when they were medicated. The authors said the data on whether it might actually be harmful to take medications for this kind of mild hypothyroidism is too poor to come to any kind of conclusion.

There's also no real downside to letting subclinical hypothyroidism go untreated. Some experts point to studies showing a higher prevalence of thyroid cancer among people with normal-yet-high TSH levels, but others say the connection is weak.

To Martin Surks, the program director of the endocrinology department at the Albert Einstein College of Medicine and chair of the 2004 panel, the two meta-analyses are a clear signal that endocrinologists shouldn't be too eager to scribble levothyroxine prescriptions for patients without true hypothyroidism. He wouldn't suggest treating a patient with Hashimoto's, normal T4 and T3, and a slightly elevated TSH, for example. With numbers like those, a person only has a small chance of developing real hypothyroidism, he said.

Once a person goes on levothyroxine, he added, they usually take it for the rest of their lives. There's a chance it could work too well—lower the TSH by too much and make the person jittery, anxious, or worse. "Such a situation is definitely associated with adverse health outcomes such as atrial fibrillation, osteoporosis, heart failure, and mortality," Surks wrote in an email.

Plus, Isaacs told me, TSH levels might not be as iron-clad as some think. They can vary widely over the course of a few months, or even within a single day. "A lot of people who are three, they come back and they're one the next time," he said.

David Cooper, a professor in the division of endocrinology at the Johns Hopkins University School of Medicine, largely agreed, but he said some individual patients who don’t meet the clinical limit might still see improvements in their health with thyroid medication. Levothyroxine is just a hormone, after all—as far as pharmaceuticals go, that's fairly harmless.

"Just because it doesn’t help 1,000 people on average, doesn’t mean that it won’t help an individual person," he said. If a person is tired and cold all the time, and their TSH is four, why not treat them? "Many physicians would say to a patient, ‘We’ll give you a therapeutic trial and see how they feel in six months.’ If they feel better, great. If they don’t, then we’ll take them off the medication. It’s not a foreign substance, it’s the same stuff your own body makes."

Cooper said he doesn't have a TSH cutoff when deciding whether to treat patients. "Even if it’s between 2.5 and four, there might be somebody I would treat who has symptoms of hypothyroidism, and someone I wouldn’t, if they feel well," he said. "If our job as doctors is to make people feel better, I see no reason not to do it."

It's amazing how even the slightest brush with hormonal drama can send a hardened skeptic wandering deep into pseudoscience land.

"I feel like all the stressors and toxins in my life are just inflaming it, you know?" I found myself saying to my boyfriend three or four times per evening. "All the crap that I've been eating because I've been too busy to cook. That's not good for the thyroid.”

The thyroid is so mysterious. The clean-eating crowd likes to think you can help it along through intricate dietary strategies, as though all the quinoa and chia seeds will form a gentle poultice at the base of the neck and nurse the ailing gland back to health. The reason Gwyneth Paltrow eats so healthily, allegedly, is that she suffers from thyroid issues and “liver congestion." Every other yoga class I attend involves some pose "that's good for the thyroid."

Others act like the thyroid is like a bald tire you have to be careful driving on: A few years ago Oprah claimed she "literally blew out my thyroid" by working too much. (In reality, you can’t really prevent hypothyroidism by eating or doing certain things. Like most things in life, luck and genes largely determine its fate).

"This whole topic of the thyroid is the biggest Internet-type thing that endocrinologists have to deal with," Isaacs told me. "There’s a huge disconnect between what’s out there on blogs and the research."

Cooper said sometimes the pressure to treat subclinical hypothyroidism comes from "angry patients who feel doctors don’t listen to them."

When he said that, I immediately thought of Dana Trentini, otherwise known as "Hypothyroid Mom." She's a woman who feels that her hypothyroidism went under-treated for years by careless doctors, and now she advocates for better testing and treatment for people with thyroid issues. She's immensely popular: Her blog gets 1.6 million monthly pageviews. She has a quarter-million followers on Facebook—more than The New Republic magazine.

I was initially wary because her blog promotes some dubious herbal remedies and treatments like oil pulling. But when I talked to her for this story, she came off as well-read and rational. More importantly, when it comes to her own case, she’s right.

Trentini was already taking medication for hypothyroidism when she got pregnant in 2009. When her doctor checked her TSH level, it would range from 5.6 and 8.6, she said—lower than the official hypothyroidism ceiling of 10. Her doctor told her the levels were normal, she says, and he kept her on the same dose of medication. Yet she felt terrible, tormented by crashing fatigue and cracking skin.

Twelve weeks into her pregnancy, Trentini miscarried.

What her doctor hadn't picked up on, for whatever reason, is that pregnant women should have a lower TSH than other people—they are the ones the 2.5 limit is intended for. The experience left Trentini wracked with guilt and rage.

"I could feel that I was very ill, but I was the kind of person who believed doctor knows best," she said. "I should have gotten a second or third opinion. I should have done something, but I didn't. The blog began because I was angry with myself."

Trentini went to see an alternative-medicine-oriented M.D., and she now takes a medication derived from pig thyroid and says she "feels fabulous." She said she's heard from hundreds of women who have had multiple miscarriages, preterm births, stillbirths, and other problems they believe were caused by under-treated hypothyroidism.

Trentini thinks her doctor and others are reluctant to aggressively treat hypothyroidism because of a "lack of interest" in following the proper guidelines. Doctors I spoke with said, on the contrary, they are interested, but there are few good studies on subclinical hypothyroidism because so little research funding goes toward non-life-threatening diseases. Others say they’re just being cautious. Unless a patient is pregnant, “observation and retesting without prescribing medications is not ‘ignoring the problem,’” Isaacs said.

But there's also a tendency, it seems, for hypothyroidism to be the disease some patients want to be diagnosed with. It's a much more satisfying explanation for fatigue, weight gain, mental fog, and depression than are the countless mental illnesses that cause many of the same symptoms. People seek solvable problems; hypothyroidism is, at least, that.

"It's always easier to prescribe a pill for someone versus saying, 'you need to see a psychiatrist or have a sleep study,'" Isaacs said. If you can fix a problem with one pill, he said, "that's the Holy Grail."