CUSHINGS-SYNDROME IN ADOLESCENTS - A DIFF ICULT ETIOLOGIC DIAGNOSIS

Endogenous Gushing's syndrome is uncommon in children and adolescents. Although no manifestation is pathognomonic, an arrest in weight and h eight gains is suggestive, Free cortisol is elevated in 24-hour urine samples collected on three consecutive days. The circadian rhythm of s erum cortisol levels is abolished, and the short or low-dose dexametha sone test shows no suppression of cortisol production. Two cases of en dogenous Gushing's syndrome are reported that illustrate the difficult y of identifying the cause. The first step is to determine whether the hypercortisolism is ACTH-dependent (normal or high ACTH levels) or AC TH-independent (low ACTH levels). Only the ACTH-dependent form is disc ussed in this article. The second step is to seek via dynamic tests to differentiate an ACTH-secreting microadenoma of the pituitary from ec topic ACTH secretion. Gushing's disease is due to increased production of ACTH by the pituitary that is only partly autonomous since it can be suppressed by high doses of dexamethasone and stimulated by CRH or metopirone. Conversely, in ectopic ACTH secretion, a very rare cause o f Gushing's syndrome, the hypercortisolism usually shows no response d uring dynamic tests. The last step of the etiologic diagnosis consists in demonstrating the lesion via imaging studies. Only in half the cas es of Gushing's syndrome is a microadenoma of the pituitary gland demo nstrable radiologically. In patients with ectopic ACTH secretion every effort should be made to identify the tumor, which is often bronchial . However, many of the lesions are small benign tumors that are diffic ult to visualize.