Risty, I am not familiar with the exact method that Cornall uses to do their ACTH stimulation test - perhaps someone who is familiar with their procedure for children, may be able to respond. Usually the test is done in the morning between 8-10am, however, again the Cornell protocol may be different.

Plasma Renin levels are usually done in addition to the ACTH stimulation test, to clarify salt-wasting status.

In response to your questions, I will paste a table from a paper, which gives a general idea of features and ranges expected, in the various degrees of severity, found in CAH. The paper from which this table comes is written by: Perrin C. White and Phyllis W. Speiser entitled, ’Congenital Adrenal Hyperplasia due to 21-Hydroxylase Deficiency’, from Endocrine Reviews, Vol 21(3), pages 245-291.

 Characteristics of different clinical forms of 21-hydroxylase deficiency

Phenotype: Classic salt wasting Classic simple virilizing Nonclassic Age at diagnosis Newborn-6m Newborn-1m 2–4 y Newborn-2 y Child-adult Child-adult Genitalia Normal Ambiguous Normal Ambiguous Normal clitoris Aldosterone Normal Normal Renin May be Normal Cortisol Normal 17-OH-progesterone >20,000 ng/dl >10,000–20,000 ng/dl 1,500–10,000 ng/dl (ACTH-stimulated) Testosterone In pre-puberty only In pre-puberty only Variably in pre-puberty only Variably Treatment Glucocorticoid mineralocorticoid ( sodium) Glucocorticoid ( mineralocorticoid) Glucocorticoid, if symptomatic Somatic growth -2-3 SD, husky-obese -1-2 SD ?-1 SD Incidence 1/20,000 1/60,000 1/1000 Typical mutations Deletion I172N V281L Large conversion nt 656g P30L nt 656g ("intron 2 g") G1108nt I236N/V237E/M239K Q318X R356W % Enzymatic activity 0 1 20–50