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By X. Ramon. Huston-Tillotson College. 2017.


Furthermore order tricor 160 mg visa, the physician may take insufficient 9 THE EVIDENCE BASE OF CLINICAL DIAGNOSIS account of the information provided by the test. For instance, studies of the consequences of routine blood testing have shown that in some cases an unaltered diagnosis still led to changes in the considered policy. For example, the MRI scan provides refined diagnostic information with regard to various brain conditions for which no therapy is yet in prospect. Finally, as discussed in the previous section, supplementary test results may not be relevant for treatment decisions. For this reason we strongly recommend that evaluation studies investigate both the discrimination of a test and its influence on management. Indication area and prior probability Whether a test can effectively detect or exclude a particular disorder is influenced by the prior probability of that disorder. A test is generally not useful if the prior probability is either very low or very high: not only will the result rarely influence patient management, but the risk of, respectively, a false positive or a false negative result is relatively high. In other words, there is an “indication area” for the test between these extremes of prior probability. For example, tests with a moderate specificity are not useful for screening in an asymptomatic population (with a low prior probability) because of the high risk of false positive results. Small steps and large numbers Compared with therapeutic effectiveness studies, evaluation studies of diagnostic procedures have often neglected the question of whether the sample size is adequate to provide the desired information with a sufficient degree of certainty. A problem is that progress in diagnostic decision making often takes the form of a series of small steps so as to gain in certainty, rather than one big breakthrough. Evaluating the importance of a small step, however, requires a relatively large study population. Changes over time and the mosaic of evidence Innovations in diagnostic technology may proceed at such a speed that a thorough evaluation may take longer than the development of even more advanced techniques.

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Testosterone Androgens effect changes in hair distribution cheap tricor 160mg visa, skin texture, stimulates muscle hypertrophy, increasing muscle mass; pitch of the voice, bone growth, and muscle development. Hair is classified by its sensitivity to androgens into non- Testosterone, in synergy with GH, causes a net increase in sexual (eyebrows and extremities); ambisexual (axilla), muscle protein. Hair follicles metabolize testos- kidneys, adipose tissue, and hematopoietic and immune terone to DHT or androstenedione. The kidneys are larger in males, and some renal the growth of facial, chest, and axillary hair; however, enzymes (e. Normal axillary and pubic hair growth triglyceride concentrations higher in men, compared to in women is also under androgenic control, whereas excess premenopausal women, a fact that may explain the higher androgen production in women causes the excessive prevalence of atherosclerosis in men. In- creased sensitivity of target cells to androgenic action, es- pecially during puberty, is the cause of acne vulgaris in The Brain Is a Target Site for Androgen Action both males and females. Most of those areas also contain ing of the vocal cords are also androgen-dependent. Eu- aromatase and many of the androgenic actions in the brain nuchs maintain the high-pitched voice typical of prepuber- result from the aromatization of androgens to estrogens. The pituitary also has abundant androgen receptors, but no The growth spurt of adolescent males is influenced by a aromatase. The enzyme 5 -reductase is widely distributed complex interplay between androgens, growth hormone in the brain, but its activity is generally higher during the (GH), nutrition, and genetic factors. Sexual dimorphism in the cludes growth of the vertebrae, long bones, and shoulders. Because of the latter, precocious puberty is as- spring, in humans, sexual activity and procreation are not sociated with a final short adult stature, whereas delayed tightly linked. Superimposed on the basic reproductive puberty or eunuchoidism usually results in tall stature. An- mechanisms dictated by hormones are numerous psycho- 664 PART X REPRODUCTIVE PHYSIOLOGY logical and societal factors. In normal men, no correlation is To establish the cause(s) of reproductive dysfunction, found between circulating testosterone levels and sexual physical examination and medical history, semen analysis, drive, frequency of intercourse, or sexual fantasies. Simi- hormone determinations, hormone stimulation tests, and larly, there is no correlation between testosterone levels and genetic analysis are performed.

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Neutrophils are an important participant in the in- 202 PART IV BLOOD AND CARDIOVASCULAR PHYSIOLOGY CLINICAL FOCUS BOX 11 discount 160 mg tricor otc. Red cell progenitors may be Many diseases result from a specific defect in the immune successfully cultivated and infused for those with certain or hematopoietic system. Platelet progenitors may be used in patients with tively treated by infusion of specific precursors of the de- one of the many forms of inborn or acquired thrombocy- fective cells, a process termed hematotherapy. In addition, this emerging therapeutic approach cal bone marrow transplant, the entire hematopoietic may soon be enhanced by genetic engineering. In this system (and, consequently, the immune system) of the re- process, new or modified genes are inserted into the grow- cipient is ablated and restored with cells from the donor. For ex- this situation, the most primitive stem cells of the immune ample, a patient may be unable to mount an appropriate or hematopoietic system are eliminated and replaced. In immune response because of the lack of a specific enzyme situations such as AIDS, thrombocytopenia, certain ane- secreted by healthy leukocytes. Stem cells of these pa- mias, and genetic immunodeficiency, however, only spe- tients may be modified in culture to eliminate this defect cific committed progenitor cells of the hematopoietic or and infused back into the patient. We may soon be able to re- hold and generate sufficient progeny, the patient’s im- place these and keep the healthy portion of the patient’s mune defect may be reversed, resulting in a cure of a once hematopoietic system intact. In recent years, much interest has focused on the isola- By far, the major clinical use of stem cells to date has tion, identification, and propagation of the stem cells of been to restore the hematopoietic system of patients various tissues. Hematopoietic stem cells have recently treated with radiation or chemotherapy for cancer. Less been grown in culture and may soon be used for thera- frequently, hematopoietic stem cells have been used to peutic purposes.

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Before these findings are apparent buy tricor 160mg cheap, bone scintigraphy may show Destruction increased uptake in the subchondral bone adjacent to arthritic cartilage. The activity represents increased bone Tumors and infections destroy trabecular and/or cortical turnover associated with cartilage turnover. Subacute and chronic osteomyelitis produce pre- ization of the cartilage requires a technique that can vi- dictable radiographic changes: cortical destruction, pe- sualize the contour of the articular surface. On standard riosteal new bone formation, reactive medullary sclero- CT examination, there is inadequate contrast between ar- sis, and, eventually, cloacae and sinus tracts. In these cas- ticular cartilage and joint fluid to visualize surface de- es, the primary role of cross-sectional imaging is staging fects, while CT arthrography using dilute contrast can the infection. For example, CT is useful for surgical plan- show even small areas of degeneration. MRI MRI is the most commonly used imaging modality to ex- can also help determine treatment in chronic os- amine degenerated articular cartilage. In patients with known chronic ization of joint fluid (or injected contrast) within chon- osteomyelitis, uptake by an inflammation-sensitive nu- dral defects at the joint surface. The accuracy of clear medicine agent (like gallium or labeled white blood MRI imaging increase for deeper and wider defects. The most although neither study is sufficiently specific enough to commonly used ones are T2-weighted fast spin-echo and preclude biopsy, especially in cases in which the causative fat-suppressed spoiled gradient recalled-echo sequences. T1-weighted spin-echo sequences are used in knees that Bones with acute osetomyelitis may be radiographical- have undergone arthrography with a dilute gadolinium ly normal for the first 2 weeks of infection. However, fat-suppressed T2-weight- CT scanning can show cortical destruction and marrow ed images have the added advantage of showing reactive edema earlier than radiographs, MRI and nuclear medi- marrow edema in the subjacent bone (analogous to the cine studies are typically the first-line studies. MR im- subchondral uptake seen on bone scans), which is often a ages show the marrow edema pattern, but to increase the clue to the presence of small chondral defects in the over- specificity, osetomyelitis should only be diagnosed when lying joint surface.

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