Janie didn't notice the changes very much at first — but her teachers did. Since starting sixth grade, Janie had become restless. She was squirmy and nervous, and it was hard for her to sit still in class. Paying attention was hard, too. Finally, Janie's teachers asked the school nurse to call her father.

Janie's dad had noticed some changes as well. She was eating more than usual. But instead of gaining weight, Janie was getting thinner. And even though it was December, she was sweating a lot.

He decided it was time for Janie to have a checkup. It didn't take Janie's doctor long to discover what was wrong. Janie had a problem with her thyroid gland. Now the doctor knew just how to help her. But first Janie had a question: What in the world is a thyroid?

What Is the Thyroid?

The thyroid (say: THYE-royd) is a gland, which is an organ that produces special chemicals called hormones (say: HOR-moans). The major hormones that the thyroid makes and releases into the bloodstream are called T4 or thyroxine (say: thy-ROKS-in) and T3 or triiodothyronine (say: try-eye-o-doe-THYE-row-neen).

All the cells in the body need thyroid hormones to work properly. These hormones control how fast the body uses up energy and are also key factors in helping kids grow.

The thyroid is shaped like a little butterfly or bow tie and it sits under the skin in the front of your neck. To find it, touch your throat in the Adam's apple area with one finger and the top of your breastbone (the flat bone that runs down the middle of your chest) with another finger. The thyroid is in that small space in between your fingers. (And it bobs up and down when you swallow. See if you can feel it!)

The thyroid works like the thermostat in your house. If the thyroid is too active and produces too much T4 and T3, it's like having a thermostat that's set too high, so the house gets overheated. If it's not active enough, it's set too low and the house is too cold. And if it's making just the right amount of thyroid hormones, then it keeps the temperature just right.

What Is Thyroid Disease?

There are two main kinds of thyroid disorder or thyroid disease. Hyperthyroidism (say: hi-per-THYE-roy-diz-em) happens when the thyroid is too active and releases too much thyroid hormone into the blood. Kids with the opposite problem have hypothyroidism (say: hi-po-THYE-roy-diz-em). In this case, the thyroid isn't active enough, so not enough thyroid hormone is being made and released into the kid's bloodstream.

Why Do Kids Get Thyroid Disease?

In most cases, doctors and scientists can't say exactly why a kid gets thyroid disease. It's not something that you can catch from someone else like a cold, and usually it isn't caused by anything you've eaten (or didn't eat) or done to your body.

A kid with thyroid disease might have inherited the condition because the tendency to get thyroid disease can run in the family. That means that a kid's mom or dad, grandparents, or other close relatives might have thyroid problems, too.

A baby can have hypothyroidism from birth if he or she is born without a thyroid gland or if the thyroid didn't develop completely before birth. And sometimes a baby's thyroid is fully developed at birth but just can't make enough thyroid hormone.

Not having enough iodine (say: EYE-o-dyne) in the diet can cause thyroid problems. Iodine is a mineral that's needed by the body to make thyroid hormone. It's found naturally in foods like seafood and milk. After scientists discovered that iodine is so important to the thyroid, it was added to most kinds of salt we use to help make sure that people get enough iodine in what they eat. Because of this, it's very uncommon for a kid in the United States to get a thyroid problem from lack of iodine.

Some medicines also can cause thyroid problems by blocking the thyroid from making enough hormone.

What Are the Symptoms of Thyroid Disease?

Kids with hyperthyroidism can feel jumpy and have trouble concentrating. Like Janie, their hearts might beat fast and their hands may tremble. They can sweat a lot and have trouble sleeping. And even though they might have more of an appetite, they often lose weight or stop gaining it as they grow. Sometimes kids with hyperthyroidism will have a wide-eyed stare all the time, as if they are frightened, and in some cases their eyes may bulge out somewhat.

Kids with hypothyroidism tend to feel tired and not have much energy. Their hearts might beat slower and they may feel cold when the temperature of the room is comfortable for everyone else. Their hair may become brittle and break off more easily, and their skin may be dry and look pale and yellowish. Constipation (infrequent, hard bowel movements) can be a problem.

Kids with hypothyroidism tend to grow more slowly and may not show the changes of puberty until they receive treatment. The doctor may suspect hypothyroidism if he or she sees that a kid's growth is not staying on track on the growth charts. Although kids with hypothyroidism may tend to gain weight more easily, thyroid disease is almost never the cause of the problem in kids who are overweight.

A goiter (say: GOY-ter) is another symptom of thyroid disease. A goiter results when the thyroid gland gets swollen, or enlarged. A goiter can happen either when the thyroid is too active or when it's not active enough.

Sometimes a lump, called a nodule (say: NOD-jool), can develop in the thyroid gland, indicating thyroid disease.

What Will the Doctor Do?

When Janie went for her checkup, the doctor examined her thyroid and found that she had a goiter. The doctor also did blood tests to check how much thyroid hormone her thyroid gland was making — it was making too much.

In most cases of thyroid problems in kids, the doctor doesn't need to do anything other than a physical examination and blood tests to find out what's wrong. But sometimes, especially if the kid has a nodule in the thyroid gland, the doctor may order other tests such as an ultrasound study or a special scan, called a thyroid scan, that's like an X-ray.

If the tests show that someone has hyperthyroidism, the doctor will usually start him or her on medicine that keeps the thyroid from making too much thyroid hormone. But if the thyroid problem doesn't go away after the person has taken the pills for about 2 years, the doctor may decide (along with the patient and the patient's family) that other treatment should be done to permanently keep the thyroid from making too much thyroid hormone. This might involve taking a medicine by mouth that destroys the thyroid gland or removing most of the gland with surgery.

Whichever treatment is used, hyperthyroidism can be controlled and its symptoms will go away. A kid who has this condition will need to have blood tests done — usually a couple of times a year — to be sure the treatment is keeping the levels of thyroid hormone in the blood normal.

Blood tests are also done to diagnose hypothyroidism. All babies are tested for hypothyroidism right after they're born, even if they don't have symptoms. It's important to treat a baby with hypothyroidism in the first few weeks of life. Otherwise, the baby won't grow and develop normally.

The good news is that hypothyroidism is easy to treat. Kids with this disease will have to take a pill every day, but their symptoms will go away. They'll usually need to take this medicine for the rest of their lives, but it's a simple way to make sure the body has enough thyroid hormone to grow and develop normally.

Kids who have been growing slowly because of hypothyroidism will usually catch up to their correct height after they're treated. They'll go through puberty the way they should, too. Kids who have hypothyroidism also will need to have blood tests to measure their thyroid hormones once or twice a year to guide their treatment.

With a little care, the thyroid and the conditions it may cause can be easily managed. The end result? You'll feel like yourself again!