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INTRODUCTION

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OBJECTIVES

After studying this chapter, you should be able to:

  • Use your knowledge to explain the underlying biochemical defects in diseases.

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INTRODUCTION

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In this final chapter, nine case histories are presented as open-ended problems for you to solve, based on what you have learnt from studying this book. No solutions are provided, and there is no discussion of the cases; all that you need to know in order to explain the problems is available elsewhere in this book.

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In many cases the patient’s clinical chemistry results are presented together with reference ranges. These may differ from problem to problem, and from the reference ranges in Table 48–3, because, as discussed in Chapter 48, reference ranges from different laboratories differ in many cases.

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CASE 1

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The patient is a 5-year-old boy, who was born in 1967, at term, after an uneventful pregnancy. He was a sickly infant, and did not grow well. On a number of occasions his mother noted that he appeared drowsy, or even comatose, and said that there was a “chemical, alcohol-like” smell on his breath, and in his urine. The GP suspected diabetes mellitus, and sent him to the Middlesex Hospital in London for a glucose tolerance test. The results are shown in Figure 57–1.

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FIGURE 57–1

Plasma glucose in the patient and a control subject after a test dose of glucose.

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Blood samples were also taken for measurement of insulin at zero time and 1 hour after the glucose load. At this time a new method of measuring insulin was being developed, radioimmunoassay (see Chapter 48), and therefore both this and the conventional biological assay were used. The biological method of measuring insulin is by its ability to stimulate the uptake and metabolism of glucose in rat muscle in vitro; this can be performed relatively simply by measuring the radioactivity in 14CO2 after incubating duplicate samples of the muscle with [14C]glucose, with and without the sample containing insulin. The results are shown in Table 57–1.

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Table Graphic Jump Location
TABLE 57–1Serum Insulin (mU/L) Measured by Biological Assay and Radioimmunoassay
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As a part of their studies of the new radioimmunoassay for insulin, the team at the Middlesex Hospital performed gel exclusion chromatography of a pooled sample of normal serum, and determined insulin in the fractions eluted from the columns both by ...

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