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Blood Testing:
Assessing control from a single blood test is very commonly used due to its convenience. However, a single test may not always reflect if there is adequate control of adrenal gland activity. One also needs to consider the time of day and the timing of doses in interpreting blood levels. Some hormone levels are also better than others in assessing treatment.
A number of hormones that reflect adrenal gland activity can be measured in the blood. These factors include ACTH, 17 hydroxyprogesterone (17 OHP), androstenedione, and testosterone. Electrolytes and renin are be used to assess mineralocorticoid replacement.
Of these different hormones, androstenedione and testosterone most closely match 24-hour 17 KS production and reflect adrenal androgen production. These hormones are especially useful in prepubertal children and females. Because testosterone levels rise in puberty in males, testosterone levels are not as useful in adolescent or adult males. In comparison with androstenedione and testosterone, 17 OHP levels can fluctuate widely and may be elevated even when there is good control. The pituitary hormone ACTH has been shown to provide a nice measure of control and is elevated 75% of the time when there is undertreatment.
For children without CAH and are not in puberty, average levels of androstenedione are 25 ng/dl, average levels of testosterone levels are 5 ng/dl, and average 17OHP levels are 50 ng/dl. During puberty, levels of these hormones rise. It is possible to achieve normal levels of these hormones in children with CAH. Yet, treating CAH to "normalize" all hormone levels, especially 17 OHP levels, can result in growth suppression and weight gain. Thus, many clinicians aim for androstenedione and testosterone levels that are normal or modestly (about 25%) above normal. Because 17 OHP levels can fluctuate widely and be elevated when there is adequate treatment, some clinicians will accept mid-day 17 OHP levels of 500-1000 ng/dl; others will aim for lower levels.
Morning levels of 17 OHP, androstenedione, and testosterone are much higher than mid-day levels, especially when there is undertreatment. This occurrence reflects the general observation that adrenal glands becoming more active in the early morning hours and at a time when the medication from the day before is wearing off. It can therefore be very useful to obtain morning hormone levels.
It has been recently shown that when there is good control of adrenal gland activity, 17 OHP levels are less than less than 600 ng/dl in the morning before medication is given and less than 200 ng/dl during the day. In undertreated individuals, 17 OHP levels average 10,000 ng/dl in the morning before the dose, and 5000 ng/dl during the day.
To measure if the child is getting enough salt and/or fludrocortisone, renin and electrolyte levels are measured. An elevated renin levels indicates a need for more salt and/or fludrocortisone. A suppressed renin suggests that the dose of salt and/or fludrocortisone is too high.