Cortisol Response To Low Dose Versus Standard Dose (Back-to-Back) Adrenocorticotrophic Stimulation Tests In Children and Adolescents With Thalassemia Major
Authors: Yassin Mohamed A. , Soliman Ashraf T , Desanctis Vincenzo 
Published: October 2019

Patients with thalassemia major(TM ), especially those with inadequate iron chelation, have high prevalence of endocrinopathies. Several studies reported a significant prevalence of subclinical “biochemical” adrenal insufficiency, ranging from 18–45%, in patients with thalassemia. This variability may be due to the different severity of TM, iron overload status, the test used for assessing adrenal function, and the cutoff value used to define subnormal cortisol response.
The low dose (LD) 1-microg (ug) ACTH test follows the insulin tolerance test (ITT) has been shown to be more closely and more sensitive than the standard ACTH test in detecting more subtle insufficiency of the hypothalamic-pituitary-adrenal axis. Therefore the 1 ug ACTH test may be more appropriate for screening for secondary AI in TM patients. Measurements of serum dehydroepiandrosterone sulfate (DHEA-S) levels during LD simulation provide additional valuable information that improves the diagnostic accuracy of LDC in patients suspected to have central adrenal insufficiency (AI).
The aim of this study was to compare cortisol and DHEA-S responses to LD and SD ACTH tests in patients with TM.

Patients and Methods
This cross-sectional controlled study was conducted at the Departments of Pediatrics and Hematology, Hamad Medical Center (HMC). 10 children and 13 adolescents (age 8 to 26 years ) were randomly recruited. They had been receiving blood transfusion at a regular basis every 4 wk. Iron chelation therapy was suboptimal in most of them. Patients were excluded if they had any other endocrine or systemic disease or drugs known to affect adrenal functions. 13 healthy children and adolescents with normal variant short stature served as controls.
Serum cortisol and DHEA-S concentrations were determined in each subject before blood transfusion both in basal condition and after low dose (LD) (1 microgram) followed by standard dose (SD) (250 micrograms) respectively) with synthetic corticotrophin beta 1-24 ACTH (Synacthen Ciba). Normal controls were a group of 13 age and sex matched normal subjects.

Results
Using a peak total cortisol cutoff level of 550 nmol/L and increments of 200 ug above basal cortisol, AI was demonstrated in 8 patients after the LD ACTH and in 2 patients after SD ACTH test and in none of the controls. Using a peak total cortisol cutoff level of 420 nmol/L and increments of 200 ug above basal cortisol, AI was demonstrated in 5 patients after the LD ACTH and in 2 patients after SD ACTH test but none of controls. All patients with biochemical AI were asymptomatic with normal serum Na and K concentrations and no history suggestive of adrenal pathology.
The peak cortisol concentrations in thalassemic patients with impaired adrenal function both after 1ug and 250 ug cosyntropin, ( 294 +/- 51 nmol/L and 307 +/- 58.6) were significantly lower than those with patients with normal ( 454 +/- 79.7 nmol/L and 546.1 +/- 92.2 nmol/L respectively) and controls (460.2 +/- 133.4 nmol/L and 554.3 +/- 165.8 nmol/L respectively). Adolescents but not children with TM had significantly lower peak cortisol concentration after SD cosyntropin test versus controls. Peak cortisol response to LD cosyntropin test was correlated significantly with peak cortisol response to SD in all patients (r = 0.83, p < 0.0001). In adolescents with thalassemia DHEA-S levels before and after LD ACTH stimulation were significantly lower and the cortisol/DHEA-S ratios significantly higher than controls.
In conclusion, the use of LD ACTH test diagnoses more adrenal abnormalities versus SD ACTH in thalassemic patients. The relatively high prevalence of AI in thalassemic adolescents necessitates that these patients have to be investigated for AI before major surgery and those with impaired cortisol secretion should receive stress doses of corticosteroids during the stressful event.

Disclosures:
No relevant conflicts of interest to declare.