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."