Hormone screening test

Physiologic Function Testing, An example of this application is the assay of thyroid hormone levels in (lie blood winch, in turn, can aid in the assessment of thyroid function. The radioactive iodine uptake test, which involves the administration of a dose of l31l (iodine-131) to the patient, is also a valuable procedure in assessing thyroid function. At present, the technique is best reserved for problem cases rather than used as a primary screening test. The main disadvantage of this test is the effect of the dietary intake of iodine, which reacts in various ways in different individuals. 

F2. Fanchin, R., De Ziegler, D., Olivennes, F., Taieb, J., Dzik, A., and Frydman, R., Exogenous follicle stimulating hormone ovarian reserve test (EFORT) A simple and reliable screening test for detecting poor responders in in-vitro fertilization. Hum. Reprod. 9, 1607-1611 (1994). 

On occasion, iodinations are not performed by the user. The talc-resin-TCA test is a simple technique for validating the suitability of I-labeled hormones obtained commercially, which often are expensive. As only the equivalent of three assay tubes of iodohormone are required for this simple screening test, it is not unreasonable to check the quality of every batch of commercially labeled material before its use, including io-dohormones supplied with RIA kits. 

Cp is most often measured as a screening test for Wilson s disease. Several other factors, including diet, hormone levels, and other genetic disorders, also influence plasma levels. Immunochemical assays may not distinguish between the active, copper-replete holoCp and apoCp, which is released into the circulation in most of the disorders associated with low total Cp levels. Functional assays might therefore be helpfiil in clinical circumstances, but they are more difficult to perform and less specific. 

Free or unbound cortisol represents the biologically active form of the circulating hormone, and its concentration is practically independent of alterations of its transport proteins. Various methods have been developed for estimating the free fraction in serum, but these assays are technically demanding, expensive, and not in general use. The measurement of urine free cortisol comes closest to providing an estimate of the free hormone concentration. As mentioned previously, approximately 2% of cortisol is excreted into the urine in a free form, and its measurement has been shown to be of use as a screening test for cortisol hypersecretion. However, P-hydroxycortisol has been reported to interfere with the immunoassay of free cortisol in urine. ... 

Total T4 and FT4E measurements are not ideal indicators of thyroid status, in part because of the effects of variations in serum binding protein concentrations, but also because T3 is the biologically active and most potent form of thyroid hormone and because the relationships between these hormones (T4 and T3) are not always predictable. In patients with hyperthyroidism, T3 is usually elevated to a greater extent than T4 because it is derived from two sources increased thyroidal secretion of T3 and increased peripheral conversion of T4 to T3. The measurement of total T3 is sometimes a useful adjunct test in patients suspected of hyperthyroidism. However, because T3 concentrations fluctuate rapidly in response to stress and other nonthyroidal factors, T3 concentrations are low not only in hypothyroidism, but also in many other conditions. Thus the routine measurement of total T3 is not a good screening test of thyroid status. 

The clinical biochemistry laboratory is commonly called upon to establish if there is excessive hormone secretion. Simple screening test.s to eliminate other diagnoses are followed by more complicated dynamic tests. If a pituitary tumour is suspected, it is important to establish the extent of damage to other pituitary functions. The combined anterior pituitary function test (Fig. 3) is used here. TRH. GnRH and insulin are given from separate. syringes. All hormones are measured at 0, 30 and 60 min, and cortisol and GH additionally at... 

Growth hormone deficiency may be present from birth or due to later pituitary-failure. A variety of stimulation tests have been used to evaluate GH deficiency. Seram GH concentrations rise in response to exercise, and this may be u.sed as a preliminary screening test. They also rise during sleep, and high concentrations in a nocturnal sample may exclude GH deficiency. The lack of GH response to clonidine, a potent stimulant of GH secretion, isdiagnostic. Some centres have now abandoned the use of insulin-induced hypoglycaemia as a diagnostic test in children because of its hazards. 

Congenital hypothyroid disorders occur with a frequency of one in every 4000 live births (pp. 144—145). If diagnosed at an early age. replacement thyroid hormone can be given and normal development can occur. Delays in treatment result in cretinism (see p. 144). Elevated T.SH, measured in blood spots, is diagnostic of disorders of the thyroid itself, i.e. primary neonatal hypothyroidism. The TSH screening test does not pick up pituitary dysfunction in the newborn. 

TSH test. Measuring the serum TSH has become the screen test of choice for thyroid disease. Primary hypothyroidism produces elevated TSH levels, whereas patients with primary hyperthyroidism (i.e., Graves disease) should have undetectable TSH values. This relationship is true only in individuals with an intact hypothalamic-pituitary-thyroid axis. Patients who present with a normal or detectable TSH level and elevated thyroid hormone concentrations require further evaluation to exclude central causes of hyperthyroidism. 

Tests to exclude possible causes of dementia include a depression screen, vitamin B12 deficiency, thyroid function tests [thyroid-stimulating hormone (TSH) and free triiodothyronine and thyroxine], complete blood cell count, and chemistry panel.21... 

Finally, a laboratory evaluation completes the initial evaluation. This includes a battery of blood tests to rule out infection, metabolic abnormality, or hormonal disturbance. It must also include a drug screen. Unfortunately, most drug screens do not detect the designer drugs like Ecstasy that are an ever-increasing cause of acute psychosis. The initial evaluation should always include a CT or MRI brain scan, preferably the latter. 

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