The thyroid gland is a butterfly shaped organ that resides in the front part of your neck, just in front of your windpipe and below your voice box. The gland normally weighs one ounce or less. In thin individuals, a portion of the gland may be palpated (felt with the fingers) through the overlying skin and muscle in the neck. In very muscular individuals or those with increased amounts of adipose tissue, the gland can be difficult or impossible to feel with the fingertips. It has a very rich blood supply, and is fed by branches of the subclavian and carotid arteries. The thyroid gland rests on top of the nerves which are responsible for moving your vocal cords. The internal thyroid architecture is composed of multiple spherical groups of cells surrounding a gelatinous material known as colloid. The spherical units are known as follicles. Colloid is a collection of protein bound to thyroid hormone. The cells forming the colloid-containing spheres (follicles) are called follicular cells. These are the most abundant cells in the thyroid.
The thyroid gland absorbs iodine from your blood stream and turns this iodine into thyroid hormone. Iodine is found in many foods and enters the body via the gastrointestinal tract. There are two important types of thyroid hormone: T3 which contains 3 iodide (iodine) molecules and T4 which contains 4 iodide molecules. The thyroid gland secretes thyroid hormone into the bloodstream and the hormone circulates throughout the body. Thyroid hormone is responsible for your body’s metabolism (breakdown of molecules to form energy) and certain forms of protein synthesis. Every cell in the body relies on thyroid hormone to regulate its metabolism. If your thyroid gland is overactive (hyperthyroid) and secreting too much hormone, you may experience rapid heart rate, palpitations, weight loss, anxiety and heat intolerance (you always feel warm). If your thyroid gland is underactive (hypothyroid) you may gain weight, become lethargic, suffer from constipation and have cold intolerance (you always feel cold).
Thyroid nodules are relatively common. Clinical studies show that ultrasound can detect thyroid nodules in 20%-76% of the general population [1,2]. Three percent to 7% of the population has a nodule that can be palpated (felt) during a routine physical examination [3,4]. Solid thyroid nodules form when one or more cells in the thyroid gland deviate from the normal cell life cycle and engage in unregulated cell division. Some nodules show steady growth, many become stable in size and others regress. Most solid nodules produce less thyroid hormone than the surrounding normal thyroid tissue. These nodules appear “cold” on a thyroid function scan. However, some nodules also display unregulated production of thyroid hormone. These nodules appear “hot” on a thyroid function scan. Hot nodules can cause hyperthyroidism. Sometimes the nodules form large follicles and contain colloid (colloid nodule)-see explanations of “follicle” and “colloid” above in “What is the thyroid gland?” Nodules may be solitary or associated with other nodules in the gland. An enlarged thyroid gland with multiple nodules is called a multinodular goiter. Very large nodules or multinodular goiters may cause an obvious cosmetic deformity in the neck, difficulty swallowing or compression of the trachea with difficulty breathing.
The vast majority of thyroid nodules are benign (not cancerous). About 1 in 20 thyroid nodules are cancerous. Cancerous nodules have the ability for the abnormal thyroid cells to invade into the surrounding thyroid tissue and spread beyond the thyroid to lymph nodes and other structures in the neck. In rare circumstances, the lungs and then other parts of the body may be invaded by thyroid cancer. Certain features are associated with an increased risk of cancer in thyroid nodules: A family history of papillary or medullary types of thyroid cancer, age less than 20 or greater than 70 years, male gender, history of head and neck radiation as a child (this was performed for acne or enlarged tonsils years ago), an enlarging or non-mobile nodule, and associated vocal cord paralysis. Unfortunately, there is no fail-safe way to distinguish benign nodules from cancerous nodules by way of physical examination or imaging (ultrasound, thyroid scan, CT scan or MRI). Furthermore, nodule size is not predictive of malignancy.
Fine needle aspiration biopsy is a useful test to help determine malignancy or increased suspicion for malignancy in a thyroid nodule. During this test, the skin overlying the thyroid gland is cleansed and anesthetized (usually injected with lidocaine). A small needle is passed through the skin and underlying soft tissue and then into the thyroid gland. The needle enters the thyroid nodule and extracts some abnormal cells. The cells are spread on to a glass slide and analyzed by a pathologist. If the thyroid nodule cells are malignant, suspicious for malignancy, or if malignancy cannot be ruled out, partial or complete removal of the thyroid gland may be discussed. Additional treatment , such as radioactive iodine, may be necessary if thyroid cancer is present. If the needle biopsy suggests a benign nodule then observation of the nodule is often undertaken. This is accomplished with follow up ultrasound to evaluate for interval growth. Significant growth between ultrasounds is concerning for malignancy.
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The parathyroid glands are 4 tiny glands located in the neck behind the the thyroid gland. They release a hormone called parathyroid hormone. Parathyroid hormone controls your body’s calcium homeostasis (balance of calcium level in the blood and cells). The parathyroid glands, through release of parathyroid hormone, control how much calcium is absorbed from food and vitamins by your gastrointestinal tract, how much calcium is excreted in the urine and how much calcium enters or leaves your bones. The most common parathyroid gland abnormality evaluated in our practice is the overproduction of parathyroid hormone which results in increased absorption of calcium from the gut, decreased calcium excretion in the urine, leaching of calcium from the bones and therefore high blood calcium levels. High levels of calcium in the blood can cause depression, anxiety, bone and muscle aches and pains as well as fatigue. Additionally, kidney stones may result. The most common cause of this disorder is an enlarged parathyroid gland or parathyroid gland tumor which is secreting too much parathyroid hormone. Treatment usually consists of surgically removing this tumor (called a parathyroid adenoma) with parathyroidectomy.