Medical brain notes 15

  THYROID GLAND   Multinodular goiter  (nontoxic goiter) refers to an enlarged thyroid gland with mul-tiple colloid nodules. Females are affected more often than males. It is frequently asymptomatic, and the patient is typically euthyroid, with normal T4, T3, and TSH.  Plummer syndrome  is the development of hyperthyroidism (toxic multinodular goi-ter) late in the course.   Microscopically, the tissue shows nodules of varying sizes composed of colloid folli-cles. Calcification, hemorrhage, cystic degeneration, and fibrosis can also be present.   Hyperthyroidism   The term  hyperthyroidism  is used when the mean metabolic rate of all cells is increased due to increased T4 or T3. Clinical features include tachycardia and pal-pitations; nervousness and diaphoresis; heat intolerance; weakness and tremors; diarrhea; and weight loss despite a good appetite. Lab studies show elevated free T4.   •        ...

  PARATHYROID GLANDS   Primary hyperparathyroidism  can be caused by the following:   •           Adenomas (80%); may be associated with MEN 1   •           Parathyroid hyperplasia (15%)   °°      Characterized by diffuse enlargement of all 4 glands; the enlarged glands are usually composed of chief cells   °°      Parathyroid carcinoma is very rare   •           Hyperparathyroidism can also occur as a paraneoplastic syndrome of lung and renal cell carcinomas.   The excess production of parathyroid hormone (PTH) leads to hypercalcemia, with lab studies showing elevated serum calcium and PTH.   Primary hyperparathyroidism  is often asymptomatic, but may cause kidney stones,   osteoporosis and osteitis fibrosa cystica, metastatic calcifications, or neurologi...

  PITUITARY GLAND, HYPOTHALAMUS, AND PINEAL GLAND   Pituitary adenomas  are categorized as follows:   •           Microadenoma  if   <1 cm   •           Macroadenoma  if   >1 cm   Macroadenomas cause visual field defects.   GNAS1  mutations are common. Pathologically, adenomas are monomorphic com-pared with normal pituitary.   •           Prolactinoma  is the most common type of pituitary adenoma. Lactotroph cells   secrete prolactin, which results in hyperprolactinemia. Clinical features include galactorrhea, amenorrhea, and infertility, or decreased libido and impotence.   •           Nonfunctional adenoma  may produce hypopituitarism.   •           Growth-hormone–produ...

  ADRENAL GLAND   Cushing syndrome  is characterized by increased levels of glucocorticoids. It is inves-tigated with lab and imaging studies. The most com-mon cause is exogenous glucocorticoid administration.   Endogenous causes include:   •           Cushing disease (hypersecretion of ACTH, usually due to a pituitary micro-adenoma)   •           Secretion of ACTH from nonpituitary tumors (e.g., small cell lung cancer)   •           ACTH-independent Cushing syndrome due to adrenal neoplasia   Clinical manifestations include hypertension, weight gain (truncal obesity, “buf-falo hump” and moon facies), cutaneous striae, hirsutism and mental disturbances. Hyperaldosteronism   may cause hypertension and hypokalemia.     •           Primary  (decreased pl...