As I far as I understand with SWCAH 21 hydroxylase deficiency, this is what is often tested and why (well ALL are tested to check control of CAH)

 

Glucocorticoid Treatment - to replace cortisol with hydrocortisone (dex or pred) 

 

17 OHP snap shot view to see if these androgens are suppressed. High levels of 17 OHP undertreatment too low levels overtreatment.

Cortisol, to see how much cortisol there is in the blood at that time, enough or too little in regard to the suppression of the 17 OHP

Androstenedione, this shows a 24 hour control of CAH (High levels show undertreatment -  too low levels shows overtreatment)

ACTH  this is released by pituitary gland in the brain and high levels of ACTH show undertreatment.

 

Mineralcorticoid treatment - to replace aldosterone with fludrocortisone

 

Electrolytes - show proper balance of salts and fluids. This checks the sodium levels, potassium levels and sees if the body is well hydrated

Renin (PRA)

This is checked to see if the aldosterone is being correctly replaced with fludrocortisone. Aldosterone is needed to get the kidney to reabsorb sodium.

Two ways of doing the test, after resting or active (each have different normal values)

High renin level means not enough fludro - dose too low

Low renin level means too much fludro - dose too high

 

Blood pressure

This can be high if the fludrocortisone or hydrocortisone replacement is too much in 21 hydrolyse deficiency -

Low blood pressure can be a sign of undertreatment.

 

Puberty Hormones

LH (Luteinizing Hormone)

FSH (Follicle Stimulating Hormone)

 

These for a girl stimulate ovaries to make estrogens

These for a boy stimulate testicles to produce testosterone

 

Testosterone is tested as this is converted to estrogens which causes bone age to advance.

 

Height

Growing too fast - dose to low

Growing too quickly - dose to high

 

Weight

Too much weight gain -can be signs overtreatment

Weight loss - can be signs of undertreament.

 

Please note this is only my understanding and you should discuss all with your doctor. It seems most doctors have a different view on what an optimal  level is and they need to look at all the results together. I hope this helps, others may be able to explain better.