The most common type of thyroid carcinoma is papillary carcinoma. About 80% to 85% of thyroid cancers are papillary carcinomas (also called papillary cancer or papillary adenocarcinoma). Papillary carcinomas develop from the thyroid follicle cells and typically grow very slowly. Usually they occur in only one lobe of the thyroid gland, but about 10% to 20% of the time both lobes are involved. Several different variants (subtypes) of papillary carcinoma can be recognized under the microscope. These include the follicular variant, tall cell variant, columnar cell variant and diffuse sclerosing variant. The usual form of papillary adenocarcinoma and the follicular variant have the same outlook for survival (prognosis), and treatment is the same for both. The other variants tend to spread more quickly and have a worse prognosis. Even though papillary cancer grows slowly, it often spreads early to the lymph nodes in the neck. Fortunately, most people with papillary cancer do not die from it.
Papillary carcinoma typically arises as an irregular, solid or cystic mass that arises from otherwise normal thyroid tissue. Prognosis is directly related to tumor size and a “good prognosis is associated with tumors less than 1.5 cm (1/2 inch) in size. This cancer has a high cure rate with ten year survival rates for all patients with papillary thyroid cancer estimated at 80-90%. Cervical metastasis (spread to lymph nodes in the neck) are present in 50% of small tumors and in over 75% of the larger thyroid cancers. The presence of lymph node metastasis in these cervical areas causes a higher recurrence rate but not a higher mortality rate. Distant metastasis (spread) is uncommon, but when it does occur the lung and bone are the most common sites. Tumors that invade or extend beyond the thyroid capsule have a worsened prognosis because of a high local recurrence rate. Surgery is the treatment for papillary cancer, which sometimes spreads to nearby lymph nodes. Nodules smaller than three quarters of an inch across are removed along with the thyroid tissue immediately surrounding them, although some experts recommend removing the entire thyroid gland. Surgery almost always cures these small cancers.
Since papillary cancer may respond to thyroid-stimulating hormone, thyroid hormone is taken in doses large enough to suppress secretion of thyroid-stimulating hormone and help prevent a recurrence. If a nodule is larger, most or all of the thyroid gland is usually removed, and radioactive iodine is often given in expectation that any remaining thyroid tissue or cancer that has spread away from the thyroid will take it up and be destroyed. Another dose of radioactive iodine may be needed to make sure the entire cancer has been destroyed. Papillary cancer is almost always cured.
Considerable controversy exits when discussing the management of well differentiated thyroid carcinomas (papillary and even follicular as described below). Some experts contend than if these tumors are small and not invading other tissues (the usual case) then simply removing the lobe of the thyroid which harbors the tumor (and the small central portion called the isthmus) will provide as good a chance of cure as removing the entire thyroid. These proponents of conservative surgical therapy relate the low rate of clinical tumor recurrence (5-20%) despite the fact that small amounts of tumor cells can be found in up to 88% of the opposite lobe thyroid tissues. They also cite studies showing an increased risk of hypoparathyroidism and recurrent laryngeal nerve injury in patients undergoing total thyroidectomy (since there is an operation on both sides of the neck). Proponents of total thyroidectomy (more aggressive surgery) cite several large studies that show that in experienced hands the incidence of recurrent nerve injury and permanent hypoparathyroidism are quite low (about 2%). More importantly, these studies show that patients with total thyroidectomy followed by radioiodine therapy and thyroid suppression, have a significantly lower recurrence rate and lower mortality when tumors are greater than 1.5cm. One must remember that it is also desirable to reduce the amount of normal gland tissue that will take up radioiodine.
Based on the these studies and the above natural history and epidemiology of papillary carcinoma, the following is a typical plan: Papillary carcinomas that are well circumscribed, isolated, and less than 1cm in a young patient (20-40) without a history of radiation exposure may be treated with hemithyroidectomy and isthmusthectomy. All others should probably be treated with total thyroidectomy and removal of any enlarged lymph nodes in the central or lateral neck areas. Thyroid cells are unique in that they have the cellular mechanism to absorb iodine to synthesize thyroid hormone. No other cell in the body can absorb or concentrate iodine. This uptake is taken advantage of in radioactive iodine treatments for thyroid cancer. Papillary cancer cells absorb iodine and therefore they can be targeted for death by giving the toxic isotope (I-131). Once again, not everybody with papillary thyroid cancer needs this therapy, but those with larger tumors, spread to lymph nodes or other areas, tumors which appear aggressive microscopically, and older patients may benefit from this therapy. This is an extremely effective type of “chemotherapy” will little or no potential adverse reactions (no hair loss, nausea, weight loss, etc.). However, the decision to use RAI should be made on an individual patient basis. Uptake is enhanced by high TSH levels; thus patients should be off of thyroid replacement and on a low iodine diet for at least one to two weeks prior to therapy. It is usually given 6 weeks post surgery (this is variable) can be repeated every 6 months if necessary (within certain dose limits).
Regardless of whether a patient has just one thyroid lobe and the isthmus removed, or the entire thyroid gland removed, most experts agree they should be placed on thyroid hormone for the rest of their lives. This is to replace the hormone in those who have nothyroid left, and to suppress further growth of the gland in those with some tissue left in the neck. There is good evidence that papillary carcinoma responds to thyroid stimulating hormone (TSH) secreted by the pituitary, therefore, exogenous thyroid hormone is given which results in decreased TSH levels and a lower impetus for any remaining cancer cells to grow. Recurrence and mortality rates have been shown to be lower in patients receiving suppression.
In addition to the usual cancer follow up, patients should receive a yearly chest x-ray as well as thyroglobulin levels Thyroglobulin is not useful as a screen for initial diagnosis of thyroid cancer but is quite useful in follow up of well differentiated carcinoma (if a total thyroidectomy has been performed). A high serum thyroglobulin level that had previously been low following total thyroidectomy especially if gradually increased with TSH stimulation is virtually indicative of recurrence. A value of greater than 10 ng/ml is often associated with recurrence even if an iodine scan is negative.
The thyroid gland is located immediately below the larynx on each side of and anterior to the trachea. It is one of the largest of the endocrine glands, normally weighing 15 to 20 grams in adults. The thyroid secretes two major hormones, thyroxine and triiodothyronine, commonly called T4 and T3. Both of these hormones profoundly increase the metabolic rate of the body. Thyroid secretion is controlled primarily by thyroid‐ stimulating hormone (TSH) secreted by the anterior pituitary gland.
About 93 per cent of the metabolically active hormones secreted by the thyroid gland are thyroxine, and 7 per cent triiodothyronine. Thyroxine is eventually converted to triiodothyronine in the tissues. Triiodothyronine is about four times as potent as thyroxine, but it is present in the blood in much smaller quantities and persists for a much shorter time than does thyroxine.
The primary function of the thyroid gland is the secretion of thyroid hormones. Thyroid gland contains the parafollicular C cells which are important for calcium metabolism.
Promotes normal growth & development & regulates energy & heat production.
Especially in the early life in the first one year because it’s deficiency will lead to mental retardation, so early detection of hypothyroidism in infancy & during birth is very crucial… when they treated we can save them from mental retardation & developmental retard at long term… so now a day’s different parts screen every day for the thyroid stimulating hormone (TSH) to find & diagnose paranodular tissue (PNT) with cretinism & congenital hypothyroidism.
So Thyroid hormone is essential for growth & mental health
Physiology or the action of thyroid hormone:
To prevent the delay in growth &mental & physical retardation so pnt with hypothyroid will have mental & physical retardation. So it is important in fetal brain and skeletal maturation.
Effects of Thyroid Hormone:
Inotropic and chronotropic effects on heart so there will be increase in heart rate & the contraction of heart will be increase by pnt may develop heart failure
Increase in sensitivity & irritability
Increase gut motility so pnt will have diarrhea
Increase in basal metabolic rate
So Pnts with hyperthyroid may lose weight because there is increase in metabolic rate & because of diarrhea.
Increases sensitivity to catecholamines
Increase bone turnover
Increase in serum glucose, decrease in serum cholesterol.
Physiology of Thyroid Gland:
The basic physiological function of thyroid gland is to secrete predominantly thyroxin (T4) & only a small amount of triiodothyronine (T3).
Production of thyroid hormones is regulated in normal gland by thyroid stimulating hormone (TSH) from the anterior pituitary gland, so it’s under the influence of TSH & the TSH is under the influence of TRH from the hypothalamus, SO we have a feedback mechanism to thyroid gland by TSH.
Hypothalamus>>>anterior pituitary gland>>>thyroid gland.
Approximately 75%-80% of T3 in blood is produced from deiodination of T4 to T3 & thyroid gland secretes only 20%- 25% of T3 so Most of T3 is mainly coming from T4.
T4 is converted to T3 peripherally.
T4 is primary released hormone but T3 is the active form
Because the active form (T3) is about 10 times more than T4 in the peripheral tissues & the blood>>> so the active form & the more active component is the T3.
Hypothyroidism occurs when too little thyroid hormone is present in the body. Symptoms include feeling tired or slow, feeling cold, depressed, drowsy or lethargic, a slow heart rate, poor memory, difficulty concentrating, muscle cramping, weight gain, husky voice, thinning hair, heavy menstrual flow, milky discharge from the breasts, and infertility.
- Hypothyroidism affects about three million people per year. It may occur when the thyroid gland function
is stopped medically or surgically. Medical causes include thyroiditis, or inflammation of the thyroid gland. An inflammation can be due to autoimmune disease (Hashimoto’s thyroiditis). Pregnancy and viral or bacterial infections can also precipitate thyroiditis. A goiter, another sign of hypothyroidism, is an abnormal enlargement of the thyroid gland. Thyroid lumps or nodules also occur in or on the thyroid gland. Most nodules (90%) are non-cancerous and do not need to be removed.
- Taking thyroid replacement hormone to ensure normal levels of energy and metabolism is the treatment for hypothyroidism. Once thyroid levels are stable, blood tests are done if symptoms reoccur, or yearly to ensure that levels have remained stable.
Manifestation of HYPOTHYROIDISM
- Cold intolerance
- Cretinism (children)
- Dry hair
- Elevated aspartate
- transaminase, alanine
- transaminase and lactate
- dehydrogenase levels
- Elevated creatine
- Inverted T waves in electrocardiogram
- Low-amplitude QRS wave in electrocardiogram
- Reduced cardiac output
- Reduced respiratory rate
- Weight gain
I. All about the thyroid
The thyroid gland, also called as thyroid, is one vital organ of the endocrine system of the body. As an endocrine gland, it secretes hormones- chemicals of the body that helps regulate cellular activities, into one’s bloodstream. The thyroid is located in the neck area, fronting the trachea. It is said to be 2 centimeters in width and 4 centimeters in height.
The thyroid gland is able to produce two hormones, thyroxine, also called T4 and triiodothyronine, also called T3. These two hormones are tasked to regulate the body’s metabolism and growth. One’s metabolism is the rate by which the body burns energy and how quick the body’s reaction is. In addition, it also affects how much on weighs and sleeps.
I. What is it?
The thyroid gland is one of the largest endocrine gland in the body that produces iodine- containing hormones called the thyroid hormones. This endocrine hormone regulates the body’s rate to which it uses energy, producing heat. It also regulates other body functions like heart rate and body temperature. In addition, the thyroid gland is also important because it facilitates development of all body tissues.
However, there are some instances that the thyroid gland becomes dysfunctional. This means that the thyroid does not function well that it may result to it’s over or under activity. With this condition, one’s overall health may be at risk. To avoid further problems, this thyroid disorder should be treated.