THE RADIOACTIVE CAPSULE IN THE PALM OF MY HAND appeared surprisingly small, almost ordinary. By then I’d memorized the guardrails of my radioactive quarantine. No conversations closer than four feet. No riding public transportation for four days. No sleeping beside my husband for at least five. And the strictest of all: no contact with my 3½-year-old son for at least a week. The goal: to radiate my thyroid literally to death.

I had been diagnosed 10 months before. As a medical reporter, I knew that my symptoms—perpetual anxiety, sudden weight loss, a racing pulse—probably weren’t benign.

Then I recalled that my mother developed hyperthyroidism in her mid-forties. The tiny thyroid gland, located in the neck, drives the body’s metabolism, influencing everything from sleep to weight loss to heart rhythms. When the thyroid becomes “hyper,” it pumps out too much hormone. The condition tends to run in families.

I was tested by my family physician, and when she called with the results, I was ridiculously relieved. I was hyper­thyroid, but the problem was fixable. Well, sort of.

I started taking propylthiouracil to inhibit the thyroid’s excess production. But the medication carried a rare but potentially life-threatening side effect that, if it develops, drastically reduces the body’s ability to fight infections. The long-term option, radioactive iodine, also came with a catch. I couldn’t get pregnant for six months and ideally 12, an eternity for a woman passing her 38th birthday. Nor was that route guaranteed. In 20% of cases, the iodine doesn’t work.

I’d love to describe a flash of epiphany, but all I knew was that I couldn’t handle perpetual limbo. When I raised a margarita to mark my 40th birthday, pregnant or not, I didn’t want to still be circling the same set of indecisions.

So we developed our radiation plan. My husband and son would visit family for a few days. When they returned, I would vanish from my own house, sneaking back at night to sleep in the efficiency apartment behind our home. For seven days, Mommy was taking “a work trip,” I told my son. I hugged them both a long time before they drove off.

Soon afterward, I left for the hospital. A clinician walked me to a small room. She gave me a quick rundown: Use disposable dishes. Flush the toilet twice after each use.

Then she opened a lead-lined suitcase on the floor. From within, she pulled a lead-lined cylinder, setting it on the counter beside her. Using a pair of tweezers, she extricated the oblong capsule and gingerly deposited it in my hand.

I must have given her a long look. She laughed, a sharp sound: “These protections are more for us than for you.”

I nodded, washing the pill down.

As I drove home, my skin felt prickly and flushed, clearly radioactive. I took a deep breath, talking myself down. The radioactive iodine wasn’t supposed to cause any discomfort, other than the sense of being untouchable and alone.

For at least 18 months, my thyroid stubbornly held on despite the radioactive assault. Then, shortly after my 40th birthday, I learned that it had finally shrunk until it was minimally active.

At last I inhabited my own body again. But my relief was mixed with sadness and anger that a tiny gland could run out the clock on my last few fertile years, my best shot at creating another life overshadowed by the desire to reclaim my own.

Where to draw the line between safeguarding your fertility and safeguarding your health? Share your thoughts here.