Hey there --
Nora has a congenital form of adrenal hyperplasia which results in a buildup of adrenal androgens. These issues typically arise earlier in life, depending on the severity of the enzyme deficiency and, therefore, symptoms (more severe deficiency means symptoms appear earlier in life). In most cases of very mild CAH, symptoms appear at some point before age 25 or 30.
Your age would indicate a secondary adrenal hyperplasia (not an enzyme deficiency), which would more likely indicated a cortisol excess as opposed to a deficiency (i.e. you won't be treated with steroids). It's hard to postulate what the cause may be, since we don't know the reason why the doctor ordered DHEAS in the first place (DHEA-S is a marker for adrenal androgen overproduction).
In the case of secondary adrenal hyperplasia, it's not only the DHEA-S that is overproduced, but every other hormone produced by the adrenal gland (cortisol, aldosterone, estrione in post-menopausal women and testosterone). DHEA-S is a precursor for testosterone.
It's hard to know what the cause of the hyperplasia is without knowing any of the circumstances. Although it appears that your DHEA-S level isn't high enough to be a red flag for an adrenal adenoma (benign tumor). These levels are usually above 7mcg/mL.
Some of the differentials might include polycystic ovarian syndrome (this causes adrenal hyperplasia later in life), benign pituitary adenomas producing ACTH (a hormone that stimulates the adrenal glands), some types of medications, etc etc etc.
It's my guess that your doctor will ask for a 24 hour urine collection for cortisol. If the result is abnormal, the next thing to do is to localize the source with a low dose overnight dexamethasone suppression test (you get 1mg dexamethasone and they check your cortisol levels in the morning). If this is abnormal, then they do a high dose overnight dexamethasone suppression test to further narrow the diagnosis.
This is my guess. I highly doubt you will be given cortisol. Congenital adrenal hyperplasia is a condition resulting in a cortisol deficiency, whereas secondary adrenal hyperplasia results in a cortisol excess from another cause.