Clinical_Rounds_in_Endocrinology_Volume_II_-_Pediatric_Endocrinology

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25. How to establish the etiological diagnosis of a patient with Cushing ’ s
    syndrome?
    The approach to establish the etiological diagnosis of a patient with Cushing’s
    syndrome is summarized in the fi gure given below (Fig. 4.8 ).

Etiological Diagnosis of Childhood Cushing’s syndrome

Plasma ACTH 2300h

Plasma ACTH

5-22pg/ml

Plasma ACTH

>22pg/ml

ACTH-dependent

Cushing’s syndrome

Pituitary MRI

Tumor visualized

i.v. CRH,HDDST

Discordant Concordant

Cushing’s disease

i.v. CRH

ACTH <20pg/ml ACTH >20pg/ml

Plasma ACTH

<5pg/ml

ACTH-independent

Cushing’s syndrome

Adrenal CT

Tumor not visualized

IPSS

No ACTH gradient

Cushing’s disease Ectopic Cushing’s

ACTH gradient

• Adrenal adenoma


• Adrenal carcinoma


• PPNAD

Fig. 4.8 Approach to a child for differential diagnosis of Cushing’s syndrome

26. What is the role of MRI in localization of pituitary tumor in children with
    Cushing ’ s disease?
    Cushing’s disease is the commonest cause of CS in children above 5 years of
    age. Majority of the ACTH-secreting pituitary tumors are microadenomas
    and the tumor is commonly <5 mm. Contrast-enhanced MRI sella is the pre-
    ferred imaging modality to localize pituitary adenoma in children with
    Cushing’s disease. On MR sellar imaging, microadenomas are visualized as
    hypointense lesions as compared to normally enhancing pituitary tissue after
    contrast administration (differential enhancement). The sensitivity of conven-
    tional CEMRI to localize a pituitary microadenoma in children is approxi-
    mately 50 %; however, despite localization on MRI, concordance rate with
    surgery is only 50 %. Recently, it has been shown that use of spoiled gradient
    recalled acquisition MRI (SPGR-MRI) is associated with improved sensitiv-
    ity (75 %) and accuracy (88 %) as compared to conventional MRI (Figs. 4.9
    and 4.10 ).

4 Childhood Cushing’s Syndrome