Dynamic function tests

Published on 01/03/2015 by admin

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Last modified 01/03/2015

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Dynamic function tests

Much of clinical endocrinology is concerned with diseases that involve either a deficiency or an excess of hormones. It is not always possible to diagnose these diseases on the basis of clinical assessment and baseline laboratory investigations. Dynamic function tests (DFTs) involve either stimulating or suppressing a particular hormonal axis, and observing the appropriate hormonal response. In general, if a deficiency is suspected, a stimulation test should be used; if excess is suspected, a suppression test is used. Often, the stimulus is an exogenous analogue of a trophic hormone; in other cases it is provided by biochemical or physiological stress, e.g. hypoglycaemia or exercise.

On subsequent pages, individual DFT procedures are discussed in the context of specific hormonal axes. Here, we describe the principles that underpin some of these DFTs, and look at aspects of interpretation. The abbreviations used for the various hormones and the tests are listed in Tables 41.1 and 41.2 respectively.

Table 41.1

Abbreviations for some hormones

Adrenocorticotrophic hormone	ACTH
Arginine vasopressin	AVP
Corticotrophin releasing hormone	CRH
Follicle stimulating hormone	FSH
Gonadotrophin releasing hormone	GnRH
Growth hormone	GH (or HGH)
Growth hormone releasing hormone	GHRH
Luteinizing hormone	LH
Parathyroid hormone	PTH
Thyroid stimulating hormone	TSH
Thyrotrophin releasing hormone	TRH
Thyroxine	T₄
Triiodothyronine	T₃

Table 41.2

Commonly used abbreviations for various dynamic function tests

IST	Insulin stress test
OGTT	Oral glucose tolerance test
SST	Short Synacthen test
DST	Dexamethasone suppression test
CAPFT	Combined anterior pituitary function test

Insulin stress test

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