About the Thyroid Gland
OVERVIEW OF THE THYROID GLAND
Where is the thyroid?
Your thyroid is a gland located at the base of your neck, just below your Adam’s apple. It is shaped like a butterfly – each wing, or lobe of your thyroid lies on either side of your windpipe.
What is the function of the thyroid gland?
The purpose of your thyroid gland is to make, store, and release thyroid hormones into your blood. These hormones, which are also referred to as T3 (liothyronine) and T4 (levothyroxine), affect almost every cell in your body, and help control your body’s functions. If you have too little thyroid hormone in your blood, your body slows down. This condition is called hypothyroidism. If you have too much thyroid hormone in your blood, your body speeds up. This condition is called hyperthyroidism.
What controls the amount of thyroid hormone produced by the thyroid gland?
The amount of thyroid hormone made by your thyroid gland is adjusted by a gland in the brain called the pituitary. Another part of your brain, the hypothalamus, helps the pituitary. The hypothalamus sends information to the pituitary gland, the pituitary in turn controls the thyroid gland.
The thyroid gland, pituitary gland, and hypothalamus all work together to control the amount of thyroid hormone in your body. With the pituitary controlling most of the action, these organs work similarly to the way a thermostat controls temperature in a room.
For example, just as the thermometer in a thermostat senses the temperature of a room, your pituitary gland constantly senses the amount of thyroid hormone in your blood. If there is not enough thyroid hormone, your pituitary senses the need to “turn on the heat”. It does this by releasing more thyroid-stimulating hormone (or TSH), which signals your thyroid to make more thyroid hormone. Your thyroid gland then makes and releases the hormone directly into your bloodstream.
Your pituitary gland then senses that there is just the right amount of thyroid hormone in your body. With your thyroid hormone levels now restored to a normal level, your pituitary slows its production of TSH back down to normal.
What are thyroid function tests?
While there are a wide variety of blood tests that can be used in the evaluation of thyroid disease, thyroid function testing usually refers to measurement of both TSH (thyroid stimulating hormone) and thyroid hormone (usually T4) in the blood stream. If the thyroid is functioning normally, the T4 and the TSH are in the normal range. If the thyroid becomes underactive (hypothyroidism) the T4 declines and the TSH rises in an attempt to make the thyroid gland make some more T4. Conversely, if the thyroid gland is overactive (hyperthyroidism), the elevated T4 is sensed by the pituitary and TSH production is decreased in an effort to try to slow down the thyroid.
What can go wrong with the thyroid gland?
Diseases of the thyroid are often classified into problems primarily involving the structure of the thyroid gland (changes in size or the development of thyroid nodules) or function of the thyroid gland (over active or underactive).
Structural problems can include an enlarged thyroid gland (goiter), a small thyroid gland (atrophic) or the development of either single nodules (solitary thyroid nodule) or multiple thyroid nodules (multinodular gland). The evaluation of structural problems of the thyroid is usually done with a thyroid ultrasound.
Functional problems of the thyroid are initially evaluated with thyroid function tests which are used to determine if the thyroid is functioning normally, over active or underactive. Often times a thyroid gland can have both a structural problem and a functional problem at the same time. So the evaluation of a thyroid condition includes careful evaluation of both the structure and function of the thyroid gland
What is a thyroid nodule?
A thyroid nodule is a collection of cells within the thyroid that grow and produce a lump. Sometimes these lumps can be felt by physical examination of the thyroid gland, but oftentimes they are detected as an incidental finding on radiology studies (such as ultrasound, MRI, or CT scan) done for an unrelated reason. Fortunately, about 90-95% of thyroid nodules are benign (not cancer).
Are thyroid nodules common?
Yes, thyroid nodules can be detected with ultrasonography in nearly 40- 50% of otherwise completely healthy adults. However, most nodules are so small that they are never discovered by the patient or doctor.
Since thyroid nodules are so common, are there any features that make a nodule more likely to be cancer?
In most patients, a thyroid cancer nodule is painless and usually the patient was unaware that the nodule was present until it was detected by the primary care provider or a radiologic study. While not usually present, several features do make it more likely for a thyroid nodule to be thyroid cancer: rapid increase in size, changes in the voice, difficulty swallowing, difficulty breathing, family history of thyroid cancer, or prior history of radiation exposure during childhood.
What types of health care professionals can evaluate my thyroid gland?
In most cases, the initial evaluation of possible thyroid problems starts with a primary care health provider. Many primary care physicians manage routine hypothyroidism quite commonly. Patients with hyperthyroidism or nodular thyroid disease are often referred to an endocrinologist for further evaluations. An endocrinologist is a physician who specializes in disease of endocrine organs such as thyroid, pituitary, adrenal, and pancreas. Sometimes patients with thyroid nodules are referred directly to surgeons who specialize in problems of the thyroid for evaluation.