You probably don't give much thought to your thyroid, but the small butterfly-shaped gland in your neck—normally measuring between 4 and 6 centimeters or 1.5 to 2.5 inches wide—has a huge impact on your entire body. The thyroid produces thyroid hormone (TH), which regulates your body's metabolism, heartbeat, temperature, mood, and other important processes—reaching out to nearly every, single cell in your body. More than 30 million Americans have a thyroid disorder and an excess of 60,000 Americans are affected by thyroid cancer annually.

If you're relatively young and otherwise healthy, you may not be too concerned with the "c" word. But I know from experience that thyroid cancer can blindside you: at age 33, I was diagnosed with the disease after my doctor discovered a lump in my neck at a routine annual physical. Here's what you should know.

RELATED: What It’s Really Like to Have Thyroid Cancer

2 in 3 cases are in people younger than 55
Though cancer in general is rare in young people, most thyroid cancer patients are younger than 55, and about 2 percent of thyroid cancers occur in children and teens.

"It is not that thyroid cancer is 'plaguing' younger people, but cancers that are common in older people, like prostate and lung, don't occur in younger people," said Dr. Melanie Goldfarb, endocrine surgeon and director of the Endocrine Tumor Program at Providence Saint John's Health Center in Santa Monica.

She also added that thyroid cancer is the number-one cancer in women ages 15 to 29 and the second most common (behind breast cancer) for women ages 30 to 39.

Women are more at risk
Women account for 75 percent of all thyroid cancer cases, but experts aren't sure why, said Dr. Steven I. Sherman, associate vice provost and clinical research chair at the University of Texas MD Anderson Medical Center in Houston.

"There is a correlation between increased risk for thyroid cancer for a woman between the puberty and menopause years, but there are no conclusive results it has anything to do with hormones," Sherman said.

Some studies suggest estrogen is a growth factor both for benign and malignant thyroid cells, further suggesting gender plays a role in the prevalence of thyroid nodules and thyroid cancer, though more research is needed to solidify this claim.

RELATED: 19 Signs Your Thyroid Isn't Working Right

Symptoms can be sneaky
"Most patients don't have symptoms, but could have discomfort in the neck or feel a lump," said Dr. Kenneth D. Burman, director of the Endocrine Section at Washington Hospital Center in Washington, DC. "Patients with medullary cancer may present with unexplained diarrhea."

I never noticed the lump in my neck until my doctor slid my fingers over it and asked, "How did you not feel this?" I remember telling her that no one ever suggested I check my neck. I was only in the habit of doing a self-exam on my breasts. When I paid more attention in the mirror, I could actually see the lump move when I swallowed. The oncologist immediately picked up on my hoarse voice, the result of the mass pressing on my trachea and vocal cords. He also asked me if I had any trouble swallowing in the past few months. I did, but never guessed that it was related to my thyroid.

There's more than one type of thyroid cancer
About 80 percent of thyroid cancers are papillary carcinomas—the most common and least aggressive cancer of the thyroid. These grow very slowly and usually develop in only one of the two lobes that make up the gland. While papillary carcinomas often spread to the lymph nodes in the neck, these cancers can usually be treated successfully and are rarely fatal.

There are several subtypes of papillary carcinoma, one being what I have: papillary-follicular variant. This unique type of cancer is found in about 25 percent of patients—it seems to present and behave in a more aggressive fashion and has a higher rate of central nodal metastasis (meaning it spreads from the thyroid to the closest lymph node, usually in the throat). When found early, this subtype has a good prognosis. (It does! I'm proof!)

The less-common types of thyroid cancer
After papillary carcinoma, the next most-common type of thyroid cancer is follicular carcinoma, which accounts for about 1 in 10 thyroid cancer cases. It's more prevalent in countries where people aren't ingesting enough iodine through their diet. While these cancers usually do not spread to lymph nodes, they can spread to other parts of the body, commonly the lungs or bones.

Next is medullary thyroid carcinoma, accounting for 4 percent of cases. This type grows in C cells, so-called because they normally produce calcitonin, a hormone involved in calcium metabolism. It is easier to control and treat if it's caught early on before it has a chance to spread to other parts of the body.

RELATED: 5 Everyday Foods That Fight Cancer

The rare and more aggressive forms of thyroid cancer
Anaplastic carcinoma makes up 2 percent of all thyroid cancer cases, and was made famous by the 2012 bestseller The Fault In Our Stars ($11; amazon.com ) (the main character, a teen with this cancer, was played by Shailene Woodley in the movie). It is thought to sometimes develop from an existing papillary or follicular cancer. This cancer often spreads quickly into the neck and to other parts of the body, and is very hard to treat.

Thyroid lymphoma is also a rare form of thyroid cancer that begins in the immune system cells in the thyroid and grows very quickly. Thyroid lymphoma typically occurs in older adults.

There are thyroid cancer risk factors
While the exact cause of most thyroid cancers is not known, several risk factors have been linked to the disease. Radiation to the head and neck is one of them, said Dr. Burman.

"It is difficult to know if any cases are specifically related to medical X-rays, however," he said.

This is interesting to me because at 14, I was diagnosed with severe scoliosis (the abnormal curvature of the spin.) I underwent dozens of X-rays of my neck and spinal cord during diagnosis, treatment, and prognosis. Did that radiation exposure give me cancer? I can only speculate.

Other risk factors include nuclear power plant accidents or weapons testing, a diet low in iodine (not a risk for most Americans), family history, and genetics.

Ultrasounds help diagnose thyroid cancer
Thyroid cancer incidence has doubled since the 1970s, but that's likely due to early surveillance and heightened awareness.

"Thyroid ultrasound was in its infancy about 30 years ago—now they are being prescribed for any swelling of the neck," said Dr. David Myssiorek, an otolaryngologist at NYU Langone Medical Center.

Similar to an ultrasound technician dropping a blob of cold lubricant on a pregnant woman's belly, the same is done on the neck region. The tool used looks exactly like the one administered to track a fetus' growth.

"An ultrasound of the neck area is performed to evaluate a thyroid for a mass," Myssiorek said. "Additionally, ultrasound may play a role in determining where and how a biopsy is obtained after localizing a thyroid nodule."

PET scans also help diagnose thyroid cancer
For a positron emission tomography (PET) scan, a radioactive substance is injected into the blood. Cancer cells absorb more of the substance than normal cells, which makes them show up on the scan. PET scans are often used to determine whether thyroid cancer has spread because it can look for cancer all over the body.

I had a PET scan before and after treatment. The 40-minute test took place on a table and scanned my entire body. I hated that I needed to remain completely still throughout the test, nor did I like when a metal plate hovered just an inch from my face.

RELATED: 19 Medical Tests Women Need

Most treatments coincide, but surgery is first
Surgery is the main treatment in nearly every case of thyroid cancer, except for some anaplastic thyroid cancers. At first, I had a thyroid lobectomy where my oncologist removed the right lobe and tumor. Further pathology determined I needed a complete thyroidectomy to remove the remaining thyroid gland. Risks involved with thyroid surgery include accidental damage to the nerves connected to your vocal cords, which can cause vocal cord paralysis, hoarseness, soft voice, or difficulty breathing.

Thyroidectomy leads to lifetime of meds
After someone has a complete thyroidectomy, they need to take medication to replace thyroid hormone to maintain the body's normal metabolism. Hormone therapy also stops any remaining cancer cells from growing by lowering TSH levels. The patient's doctor tests hormone levels with a blood test every few months until the proper dosage of medication is determined.

Radioactive iodine treatment is common
Radioactive iodine treatment (RAI) is often used after the thyroid is removed to destroy any remaining thyroid tissue, as well as microscopic areas of thyroid cancer that weren't removed during surgery. The dose is taken in pill or liquid form and patients are required to be isolated from other people for at least three to five days.

Before undergoing this type of therapy, patients are advised to go on a low iodine diet to ultimately starve their body of iodine, an element that is essential for the production of thyroid hormone. When iodine is reintroduced through RAI it will kill remaining thyroid tissue and cancer cells.

"Think of thyroid tissue like a sponge," Sherman said. "For a sponge to soak up a maximum amount of water, first it must be wrung out of all the water it already contained."

Chemo and external beam radiation therapy aren't as common
"Both of these therapies are not commonly used to treat thyroid cancer," said Khoi Dao, medical oncologist with Comprehensive Cancer Centers of Nevada. "Chemotherapy may benefit some people with thyroid cancer who don't respond to RAI."

Chemo is administered as an infusion through a vein to kill cancer cells using chemicals. "External beam radiation therapy may be an option if you can't undergo surgery and your cancer continues to grow after radioactive iodine treatment," Dao said.

Another treatment is called "alcohol ablation." This involves injecting small thyroid cancers with alcohol using guided ultrasound imaging to ensure precise placement of the injection. "This treatment is helpful for treating cancer that occurs in areas that aren't easily accessible during surgery and is not widely used to treat thyroid cancer," Dao said.

Sometimes thyroid cancer may be called a "good" cancer
The five-year survival rate is 98 percent when papillary, follicular, and medullary thyroid cancers are caught early and has not spread past the gland. There are fewer than 2,000 deaths in the U.S. due to thyroid cancer each year. This is encouraging news to thyroid cancer survivors and newly diagnosed patients. That said, as someone in the trenches, it doesn't make treatment any easier. Hearing the words "You have cancer" is a life-altering blow.

"I have yet to discover a 'good' cancer," Myssiorek said. "Admittedly [thyroid cancers] are less aggressive, but anyone who says they are good, doesn't have one."

Self-examining your neck is advisable and easy
Myssiorek said to feel for the Adam's apple in your neck, the bulky cartilage that moves up and down when you swallow. Slide your fingers down until you feel the next prominent cartilage. Then place your fingers on either side of that prominence (just above the notch at the base of the neck) and swallow. If you have a problem, you should be able to feel lumps. Don't wait—see a doctor, fast.

RELATED: 27 Mistakes Healthy People Make

This article originally appeared on Health.com.