Term
| what characterizes the etiologies of hyperthyroidism? |
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Definition
| hyperthyroidism can be due to intrinsic thyroid disease or extra-thyroidal stimuli, but the 3 most common causes are due to *hyperfunction of the gland itself: diffuse hyperplasia of the thyroid due to graves disease, hyperfunctional multinodular goiter (usually unilateral), and hyperfunctional adenoma of the thyroid |
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Term
| what is hyperthyroidism essentially? |
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Definition
| a hypermetabolic state due to excess thyroid hormone featuring an overactive sympathetic nervous system (sweating/tachycardia) and an increased basal metabolic rate. |
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Term
| what is often the chief complaint for pts w/hyperthyroidism? |
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Definition
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Term
| how do pts w/hyperthyroidism often appear? |
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Definition
| the pt's skin may be warm/flushed due to increased blood flow from vasodilation in an attempts to lose heat (heat intolerance), they may be sweating and experiencing weight loss (despite appetite increase). |
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Term
| what are the cardiac effects of hyperthyroidism? |
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Definition
| increased cardiac output, tachycardia, palpitations, cardiomegaly, arrhythmias (esp Afib in elderly pts), and myocardial changes (fibrosis, fatty changes, lymphocytic infiltration). these are early and consistent features of hypothyroidism. |
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Term
| what are the neuromuscular effects of hyperthyroidism? |
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Definition
| tremors (may look like parkinson's), hyperactivity, proximal muscle weakness, and decreased muscle mass (catabolized by high metabolism) |
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Term
| what are the psychologic effects of hyperthyroidism? |
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Definition
| hyperactivity (similar to ADHD/bipolar), insomnia, anxiety, and emotional liability (angry to tearful quickly) |
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Term
| what are the ocular manifestations of hyperthyroidism? |
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Definition
| a wide staring gaze, lid lag, eyes don't close easily or completely (due to overstimulation of levator palpebrae superioris) and in grave's disease: accumulation of loose connective tissue behind the eyeballs causes them to be protuberant. |
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Term
| what are the GI effects of hyperthyroidism? |
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Definition
| overstimulation of the gut, hypermobility, malabsorption, and diarrhea (all of which can lead to muscle wasting/wt loss/neuromuscular issues) |
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Term
| what are the skeletal effects of hyperthyroidism? |
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Definition
| hyperthyroidism stimulates bone resorption and reduces the volume of trabecular bone/increases the porosity of cortical bone = osteoporosis w/increased fracture risk. |
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Term
| how does hyperthyroidism affect skeletal muscle? |
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Definition
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Term
| how are various organs in the body generally affected by hyperthyroidism? |
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Definition
| fatty infiltration (lack of protein = less lipoprotein to remove fat from various organs), lymphocytic infiltration, lymphoid hyperplasia, and lymphadenopathy (hypermetabolic state = increased lymphocyte production) |
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Term
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Definition
| an abrupt onset of severe hyperthyroidism usually associated w/graves disease. thyroid storms feature acute catecholamine elevations, tachycardia, febrility and are considered medical emergencies as some pts may die of cardiac arrhythmias. |
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Term
| what do lab studies for hyperthyroidism usually show? |
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Definition
| TSH levels are usually increased - but may be low depending on etiology (struma ovarii will have low TSH, pituitary associated will have normal/elevated TSH) and *increased free T4 OR decreased T4 w/increased T3 |
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Term
| what characterizes hypothyroidism? |
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Definition
| this is due to a structural or functional problem which interferes w/the production of thyroid hormone. incidence increases w/age and is more common in women. hypothyroidism may result from a defect anywhere in the HPA and is divided in to primary and secondary types depending on if the etiology is in the thyroid, the hypothalamus or pituitary. |
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Term
| what characterizes congenital hypothyroidism? |
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Definition
| globally, this is more common in iodine deficient areas, but may also be due to inborn errors of thyroid metabolism, thyroid agenesis or thyroid hypoplasia. |
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Term
| what characterizes aquired hypothyroidism? |
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Definition
| this may be due to sx, radiation, or drugs (done intentionally to decrease thyroid secretion) |
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Term
| what characterizes autoimmune hypothyroidism? |
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Definition
| this is the most common cause of hypothyroidism in iodine sufficient areas of the world - most of which are hashimoto thyroiditis where anti-microsomal, anti-thyroid peroxidase and anti-thyroglobulin Ab are produced against self. |
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Term
| what is secondary hypothyroidism? |
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Definition
| this can be caused by disorders of the pituitary or hypothalamus and is due to TSH or TRH deficiency |
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Term
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Definition
| hypothyroidism which develops in infancy/early childhood = impaired development of the skeletal and central nervous system = metal retardation, short stature, coarse facial features, protruding tongue, umbilical hernia. this used to occur commonly in iodine-deficient parts of the world and may occur due to inborn errors of metabolism. |
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Term
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Definition
| hypothyroidism in older child/adult featuring slowing of physical/mental activity, fatigue, apathy, depression, cold intolerance, obesity, cold/pale skin, decreased sweating, constipation, reduced cardiac output, an *atherogenic profile w/increased total cholesterol and LDL*, accumulations of *matrix substances in subcutaneous tissue/visceral sites = *non-pitting edema, coarseness of facial features, enlargement of the tongue, and deepening of the voice. TSH levels are *elevated in primary hypothyroidism but not in secondary (hypothalamic/pituitary), however *T4 levels are decreased in all types of hypothyroidism. |
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Term
| what are the different kinds of thyroiditis? |
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Definition
| hashimoto, granulomatous, and subacute lymphocytic |
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Term
| what characterizes hashimoto thyroiditis? |
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Definition
| this autoimmune inflammatory disorder affects mainly females 45-65 y/o and features activation of *thyroid specific CD4 T cells which induce formation of *CD8 T cells and *autoantibodies (results in lymphocytic infiltration). it eventually causes hypothyroidism, but initially may cause hyperthyroidism. |
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Term
| what is the pathogenesis of hashimotos? |
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Definition
| anti-TSH Ab block the action of TSH = hypothyroidism (TSH levels still may be high). the parenchyma thus develops a dense lymphocytic infiltrate *w/germinal centers (looks like a lymph node). |
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Term
| what genetically is associated w/hashimoto's? |
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Definition
| polymorphisms of cytotoxic T lymphocyte-associated-4 (CTLA4), which is a negative regulator of T cell responses |
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Term
| what are the clinical features of hashimotos? |
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Definition
| symmetric and diffuse painless enlargement of the thyroid which occurs gradually. there might be an initial transient hyperthyroidism due to a disruption of the follicles w/secondary release of thyroid hormone - at this point TSH is lowered. as hypothyroidism occurs, T3/4 levels fall concurrently w/a rise in TSH. |
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Term
| what are pts w/hashimoto at an increased risk for? |
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Definition
| other autoimmune diseases such as DM, SLE, and myasthenia gravis as well as B-cell non-hodgkin lymphoma (*especially marginal zone lymphomas of MALTs) due to increased lymphocytic infiltration. |
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Term
| how would the thyroid appear microscopically in a hashimotos pt? |
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Definition
| normal thyroid follicles near lymphocytes with germinal centers (similar to lymph node) |
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Term
| what characterizes nonspecific lymphocytic thyroiditis? |
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Definition
| this appears as multifocal lymphocytic infiltrate, causing mild symmetric enlargement often in middle aged females who in many cases have *no clear hx of thyroid disease*. |
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Term
| what is subacute/quervain's thyroiditis? |
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Definition
| in this the thyroid is enlarged - however it is due to *neurophilic infiltrate (rather than lymphocytic) which becomes a *granulomatous inflammatory reaction w/giant cells*. this also occurs mainly in females, but a slightly younger set, and cases are often preceded by upper respiratory infections. pts w/this will usually present w/neck pain, fever and transient hyperthyroidism - but it is generally self-limiting. |
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Term
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Definition
| an autoimmune disease where Ab are produced against TSH receptors and thyroid hormone, however these Ab stimulate epithelial cell activity = thyroid function (hyperthyroidism). it usually involves young females who present w/muscle weakness, wt loss, pretibial myxedema and tachycardia, and diffuse enlargement of the thyroid gland. |
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Term
| what clinical features are associated w/graves disease? |
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Definition
| opthalmopathy (soft tissues of the orbits are edematous from mucopolysaccharides), dermopathy (thickening of the dermis from mucopolysaccharides), decreased TSH, and elevated T3/4 (send negative feedback). |
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Term
| how do the follicles appear histologically in graves disease? |
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Definition
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Term
| what is a thyroid goiter? |
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Definition
| this reflects impaired synthesis of thyroid hormone - often due to dietary deficiency of iodine. impairment of thyroid hormone synthesis leads to a rise in TSH = overstimulation of thyroid tissue to the point of hypertrophy/hyperplasia (increasing dysfunction). nodules may then appear scattered throughout the goiter and cause hyperthyroidism. as the goiter enlarges it may cause dysphagia/airway obstruction/vascular obstruction. |
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