Endocrine Abstracts

Introduction: Dexamethasone Suppression Test (DST) is a useful approach in diagnosis and differential diagnosis of Cushing Syndrome (CS) despite its limitations. One of the major limitations is the difficulty to provide standard suppression dose depending on the variability of gastrointestinal absorption. One solution is for this testing serum Dexamethasone levels or test it with intravenous (iv) Dexamethasone In this case, we examined 3 patients to whom we applied intravenous DST in our clinic in 2019.

Case1

The patient who underwent left surrenalectomy and two pituitary surgeries due to Cushing Syndrome was referred to us. The Pituitary gland was showed as a thin line at pituitary MRI. Abdominal MRI was normal. The Diurnal Rhythm was preserved. The 24-hour urine cortisol was normal. 1mg DST suppression wasn’t detected. The patient had low st4 level (0.63) whe thought it might be because of intestinal edema-induced absorption disorder and whe did IV overnight DST. (1mg/st iv DXM infusion between 23:00 and 03.00) CS was not considered in the patient who have cortisol suppression.

Case2

A 49-year-old female patient who had weight gain complaint had central obesity and proximal muscle weakness. Her cortisol rhythm was impaired. Night saliva cortisol and 24-hour urine cortisol were normal. There were no 1mg DST, 2-day 2 mg DST, and 2-day 2 mg DST + CRH suppressions. A 7 × 8 mm nodular lesion was detected at Pituitary MRI. The patient with longterm diarrhea underwent IV DST considering that she might have absorption disorder. The 0 th-24 th-hour ACTH and cortisol values were used in diagnosis. The results were interpreted in favor of Cushing Syndrome (CS).

Case3

A 58-year-old female patient with surrenal adenoma didn’t have 1 mg DST, 2-day 2 mg DST suppression. Her cortisol rhythm was preserved. The 24-hour urine cortisol and saliva cortisol were normal. The 0th-24th-hour ACTH and cortisol values were used in the diagnosis (1 mg/S.D × m infusion between 1100 h and 1500 h) Since there were no suppression in the cortisol levels, sub-clinical CS was considered.

Discussion: There are limited studies on IV DST Test. There is no complete consensus on the application protocol and the diagnostic threshold value yet.

The efficiency of the IV DST Test was interpreted as an expected result because the two case both had gastrointestinal malabsorbsiyon. The third case, hadn’t malabsorbsiyon. The serum dexamethasone levels couldn’t be tested during oral DST was performed.

IV DST should be remember as patient with absorption disorders or use drugs that affect the dexamethasone metabolism.