Chap 18, Endocrine System, Pathology Flashcards
goiter
Enlargement of the thyroid gland. Low iodine levels in diet lead to low T3 and T4 levels. This causes feedback to the hypothalamus and adenohypophysis, stimulating them to secrete releasing factors and TSH. TSH then promotes the thyroid gland to secrete T3 and T4, but because there is no iodine available, the only effect is to increase the size of the gland (goiter). Prevention includes increasing the supply of iodine (as iodized salt) in the diet.
endemic goiter
Enlargement of the thyroid gland. Occurs in certain regions where there is a lack of iodine in the diet. Low iodine levels in diet lead to low T3 and T4 levels.
nodular or adenomatous goiter
Hyperplasia occurs as well as formation of nodules and adenomas. Some patients with nodular goiter develop hyperthyroidism with clinical signs and symptoms such as rapid pulse, tremors, nervousness, and excessive sweating. Treatment is with thyroid-blocking drugs or radioactive iodine to suppress thyroid functioning.
hyperthyroidism
Overactivity of the thyroid gland; thyrotoxicosis.
The most common form of this condition is Graves disease (resulting from autoimmune processes). Because metabolism is faster, the condition is marked by an increase in heart rate (with irregular beats), higher body temperature, hyperactivity, weight loss, and increased peristalsis (diarrhea occurs). In addition, exophthalmos (protrusion of the eyballs, or proptosis) occurs as a result of swelling of tissue behind the eyball, pushing it forward. Treatment of Graves disease includes management with antithyroid drugs to reduce the amount of thyroid hormone produced by the gland and administration of radioactive iodine, which destroys the overactive glandular tissue.
hypothyroidism
Underactivity of the thyroid gland.
Any of several conditions can produce hypothyroidism (thyroidectomy, thyroiditis, endemic goiter, destruction of the gland by irradiation), but all have similar physiologic effects. These include fatigue, muscular and mental sluggishness, weight gain, fluid retention, slow heart rate, low body temperature, and constipation. Two examples of hypothyroid disorders are myxedema and cretinism.
myxedema
Advanced hypothyroidism in adulthood. Atrophy of the thyroid gland occurs, and practically no hormone is produced. The skin becomes dry and puffy (edema) because of the collection of mucus-like (myx/o = mucus) material under the skin. Many patients also develop atherosclerosis because lack of thyroid hormone increases the quantity of blood lipids (fats). Recovery may be complete if thyroid hormone is given soon after symptoms appear.
cretinism
Extreme hypothyroidism during infancy and childhood leads to a lack of normal physical and mental growth. Skeletal growth is more inhibited than soft tissue growth, so the affected person has the appearance of an obese, short, and stocky child. Treatment consists of administration of thyroid hormone, which may be able to reverse some of the hypothyroid effects.
thyroid carcinoma
Cancer of the thyroid gland.
hyperparathyroidism
Excessive production of parathormone. Hypercalcemia occurs as calcium leaves the bones and enters the bloodstream, where it can produce damage to the kidneys and heart. Bones become decalcified with generalized loss of bone density (osteoporosis) and susceptibility to fractures and formation of cysts. Kidney stones can occur as a result of hypercalcemia and hypercalciuria. The cause is parathyroid hyperplasia or a parathyroid tumor. Treatment is resection of the overactive tissue. Medical therapy is another option for the patient who is not a surgical candidate. Bisphosphonates, such as alendronate (Fosamax), decrease bone turnover and decrease hypercalcemia.
hypoparathyroidism
Deficient production of parathyroid hormone. Hypocalcemia results as calcium remains in bones and is unable to enter the bloodstream. This leads to muscle and nerve weakness with spasms of muscles, a condition called tetany (constant muscle contraction). Administration of calcium plus large quantities of vitamin D (to promote absorption of calcium) can control the calcium level in the bloodstream.
adrenal virilism
Excessive secretion of adrenal androgens. Adrenal hyperplasia or more commonly adrenal adenomas or carcinomas can cause virilization in adult women. Signs and symptoms include amenorrhea, hirsutism (excessive hair on the face and body), acne, and deepening of the voice. Drug therapy to suppress androgen production and adrenalectomy are possible treatments.
Cushing syndrome
Group of signs and symptoms produced by excess cortisol from the adrenal cortex. A number of signs and symptoms occur as a result of increased cortisol secretion, including obesity, moon-like fullness of the face, excess deposition of fat in the thoracic region of the back (so-called buffalo hump), hyperglycemia, hypernatremia, hypokalemia, steoporosis, virilization, and hypertension. The cause may be excess ACTH secretion or tumor of the adrenal cortex. Tumors and disseminated cancers can be associated with extopic sectretion of hormone, such as extopic ACTH produced by nonendocrine neoplasms (lung and thyroid tumors).
In clinical practice, most cases of Cushing syndrome result from chronic use of cortisone-like drugs, such as steroids. Examples are the cases in young athletes seeking to improve their performance and in patients treated for autoimmune disorders, asthma, kidney, and skin conditions. Steroids (prednisone is an example) are never discontinued abruptly because the adrenal cortex and pituitary gland (ACTH producer) need time to “restart” after long periods of prescribed cortisol use (the adrenal gland stops producing cortisol when cortisol is given as therapy).
Addison disease
Hypofunctioning of the adrenal cortex. The adrenal cortex is essential to life. When aldosterone and cortisol blood levels are low, the patient experiences generalized malaise, weakness, muscle atrophy, and severe loss of fluids and electrolytes (with hypoglycemia, low blood pressure, and hyponatremia). An insufficient supply of cortisol signals the pituitary to secrete more ACTH, which increases pigmentation of scars, skin folds, and breast nipples (hyperpigmentation).
Primary insufficiency is believed to be due to autoimmune adrenalitis. Treatment consists of daily cortisone administration and intake of salts or administration of a synthetic form of aldosterone.
pheochromocytoma
Benign tumor of the adrenal medulla; tumor cells stain a dark or dusky (phe/o) color (chrom/o).
The tumor cells produce excess secretion of epinephrine and norepinephrine. Signs and symptoms are hypertension, tachycardia, palpitations, severe headaches, sweating, flushing of the face, and muscle spasms. Surgery to remove the tumor and administration of antihypertensive drugs are possible treatments.
hyperinsulinism
Excess secretion of insulin causing hypoglycemia. The cause may be a tumor of the pancreas (benign adenoma or carcinoma) or an overdose of insulin. Hypoglycemia occurs as insulin draws sugar out of the bloodstream. Fainting spells, convulsions, and loss of consciousness are common because a minimal level of blood sugar is necessary for proper mental functioning.