Endocrine tests and their normal values

Reference to Fig. 9.1 will indicate the format to be followed in this chapter. Assays have been set up for almost all of the hormones mentioned but only some are used in routine clinical practice.

Hypothalamic hormones

Because of the discrete nature of the communication between the hypothalamus and the pituitary, and because many of the hypothalamic hormones are not made exclusively in that region, measurements of them in the systemic circulation are rarely helpful. GHRH and somatostatin, for example, are gut hormones. Assays for many of these hormones do exist but are mainly for use in those rare patients who may have tumours secreting hypothalamic hormones.

Pituitary hormones

Assays of all the pituitary hormones are common and a sampling protocol in common use for testing pituitary function is shown in Table 10.1. The administration of intravenous insulin to lower blood glucose concentration is potentially hazardous. A reliable indwelling cannula must be inserted and a physician who must not be allowed to be called away for any reason whatsoever has to remain with the child throughout the procedure. For this reason, it may be difficult safely to perform such tests in a hospital where there is also responsibility for that physician to attend an emergency or obstetric department.

If a child becomes symptomatically and biochemically hypoglycemic (blood glucose concentration < 2mmol/l), an adequate stimulus to GH and ACTH secretion should have been applied and glucose should be administered while sampling to measure hormone concentrations continues.