Clinical_Rounds_in_Endocrinology_Volume_II_-_Pediatric_Endocrinology

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19. How to approach a child with suspected Cushing ’ s syndrome?

An approach to a child with suspected Cushing’s syndrome is depicted in the

fi gure given below (Fig. 4.7 ).

20. What is the role of estimation of 0800 – 0900h cortisol in the diagnosis of
    Cushing ’ s syndrome?
    Estimation of 0800–0900h cortisol is helpful in the differentiation of exoge-
    nous from endogenous Cushing’s syndrome, as it is suppressed in patients with
    exogenous Cushing’s syndrome. This is important because rampant use of
    alternative medications is not uncommon in clinical practice. Baseline morning
    cortisol is also required for the interpretation of HDDST, as well as for the
    assessment of circadian rhythm.


21. How to perform dexamethasone suppression tests in children?

The dose of dexamethasone used for various suppression tests in the diagnosis

of childhood Cushing’s syndrome are summarized in the table given below. The

diagnostic cutoffs of serum cortisol after dexamethasone suppression tests are

same as in adults. However, it should be noted that ONDST is less preferred in

children.

Suspected Childhood Cushing’s Syndrome

Measure 0800-0900h Plasma Cortisol

<100nmol/L 100-350 nmol/L >350 nmol/L

Perform any one test

UFC b

If abnormal

Confirm by performing one more test

Results of 2 tests

Concordant Discordant

Endogenous hypercortisolemia Needs further evaluation

Plasma cortisol >350 nmol/L with exogenous Cushing’s,

if on hydrocortisone a

To be repeated twice b

2300h cortisol c

LDDST Midnight cortisol c

Exogenous Cushing’s a •Exogenous Cushing’s with recovering

HPA axis

•Mild Cushing’s syndrome (e.g. PPNAD)

•Cyclical Cushing’s syndrome

Fig. 4.7 Approach to a child with suspected Cushing’s syndrome

4 Childhood Cushing’s Syndrome