Happy New Year! I hope your holidays were joyful – and safe. January is generally the time when we set our priorities for the year. Many of us make resolutions to improve our bodies on the outside, such as losing weight. But here, we’re going to take a closer look at our bodies on the inside. Today, we’re going to think about our thyroids.

The thyroid is a gland that’s part of the body’s endocrine system. It’s responsible for making and releasing a steady amount of thyroid hormones into the bloodstream. These hormones regulate metabolism, the process of breaking down the food you eat into energy. Your metabolism affects how fast your body performs its daily functions.

Thyroid hormones regulate many body processes. These include your breathing, heart rate, body weight, temperature, cholesterol level, muscle strength and even women’s menstrual cycles. It’s important that these hormones stay at a consistent level in your bloodstream.

The thyroid is shaped a little like a butterfly and sits at the base of your throat just below your voice box. It’s about two inches long and has two lobes that lie on either side of your windpipe. The lobes are connected by a small strip of tissue called an isthmus.

The main hormones produced by the thyroid are triiodothyronine or T3 and thyroxine or T4. T3 and T4 are made by special cells called follicular epithelial cells. The thyroid also makes calcitonin in its C-cells.  Calcitonin regulates the amount of calcium and phosphorus in your blood and inhibits the breakdown of your bones.

The amount of T3 and T4 in your blood is controlled by two other glands, the pituitary in the center of the skull below the brain, and the hypothalamus in the brain. The hypothalamus produces a hormone that signals the pituitary to release its thyroid stimulating hormone (TSH). TSH tells the thyroid to release more or less T3 and T4 to maintain a balance.

When there’s an imbalance, too much or too little T3 and T4 in your blood, your body reacts. Too little thyroid hormone is a condition called hypothyroidism. It occurs when your thyroid doesn’t make enough of its hormones. Too much thyroid hormone is called hyperthyroidism.

With hypothyroidism, your metabolism slows down. Common symptoms include weight gain, sluggishness, fatigue, dry skin and hair, intolerance to cold, and depression. With hyperthyroidism, your metabolism speeds up. Symptoms include irritability, racing heartbeat, muscle weakness, weight loss and sleep problems.

There are multiple causes of thyroid disorders like hypothyroidism and hyperthyroidism. Hypothyroidism may be caused by inflammation of the thyroid gland that can lower the amount of hormones produced or by a hereditary disease of the immune system called Hashimoto’s thyroiditis. An iodine deficiency can affect the production of thyroid hormone as well.3 Removal of the thyroid also gives you hypothyroidism.

Causes of hyperthyroidism include Grave’s disease, a condition in which the entire thyroid is overactive. Sometimes, just one or a few nodules inside the thyroid produce too much hormone. Too much iodine can cause some people to have too much thyroid hormone and some to have too little.

Treatment of these disorders focuses on restoring normal blood levels of the thyroid hormones. Treatment for hypothyroidism is hormone replacement with a synthetic version in pill form. Your doctor will monitor your hormone levels with periodic blood tests and adjust your dose accordingly.

Treatment for hyperthyroidism is a little trickier. To normalize hormone levels, your doctor may use medications to block hormone production or radioactive iodine to disable your thyroid. Another treatment option is removal of the thyroid. This will give you hypothyroidism, as can the radioactive iodine. Then, you’ll have to take the hormone replacement therapy.

Thyroid disorders, including hypothyroidism, are lifelong conditions. But by following your doctor’s instructions and having your hormone levels monitored regularly, you can still live a normal, healthy life.